1. What is an atom?
An atom is the smallest unit of an element.
2. Why is an atom neutral?
It has equal protons and electrons.
3. What is a proton?
A proton is a positively charged particle in the nucleus.
4. Why do protons define an element?
Protons determine the atomic number.
5. What is an electron?
An electron is a negatively charged particle outside the nucleus.
6. Why do electrons orbit the nucleus?
Electrons are attracted to protons’ positive charge.
7. What is a neutron?
A neutron is a neutral particle in the nucleus.
8. Why do neutrons affect mass?
Neutrons add to the atom’s mass.
9. What is the nucleus?
The nucleus is the atom’s dense core with protons and neutrons.
10. Why is the nucleus positive?
It contains positively charged protons.
11. What is atomic number?
Atomic number is the number of protons.
12. Why is atomic number unique?
Each element has a distinct proton count.
13. What is mass number?
Mass number is protons plus neutrons.
14. Why does mass number vary?
Neutron numbers differ in isotopes.
15. What is an isotope?
Isotopes have same protons, different neutrons.
16. Why is carbon-12 an isotope?
It has six protons and six neutrons.
17. What is an isobar?
Isobars have same mass number, different protons.
18. Why are argon-40 and calcium-40 isobars?
Same mass number, different atomic numbers.
19. What is Thomson’s model?
Thomson’s model shows electrons in a positive sphere.
20. Why is it called plum pudding?
Electrons are like plums in positive pudding.
21. What is Rutherford’s model?
Rutherford’s model has a nucleus with orbiting electrons.
22. Why did Rutherford propose a nucleus?
Alpha scattering showed a dense core.
23. What is Bohr’s model?
Bohr’s model has electrons in fixed orbits.
24. Why did Bohr suggest orbits?
Orbits explain stable electron paths.
25. What is an electron shell?
A shell is where electrons orbit.
26. Why do shells have energy levels?
Electrons have specific energies in shells.
27. How many electrons can the first shell hold?
The first shell holds 2 electrons.
28. Why does the first shell hold 2 electrons?
It follows the 2n² rule for n
29. What is the K shell?
The K shell is the first shell.
30. Why is the K shell nearest the nucleus?
It has the lowest energy.
31. What is the L shell?
The L shell is the second shell.
32. Why can the L shell hold 8 electrons?
For n
33. What is the M shell?
The M shell is the third shell.
34. Why can the M shell hold 18 electrons?
35. What is a valence electron?
A valence electron is in the outermost shell.
36. Why do valence electrons matter?
They determine chemical properties.
37. What is the valence shell?
The valence shell is the outermost shell.
38. Why does the valence shell affect reactions?
It holds electrons for bonding.
39. Who discovered the electron?
J.J. Thomson discovered the electron.
40. Why was the electron’s discovery important?
It showed atoms have smaller parts.
41. Who discovered the proton?
Ernest Rutherford discovered the proton.
42. Why was the proton’s discovery significant?
It explained the positive charge in atoms.
43. Who discovered the neutron?
James Chadwick discovered the neutron.
44. Why was the neutron’s discovery key?
It explained atomic mass differences.
45. What is the charge of a proton?
A proton has a +1 charge.
46. Why is a proton positive?
It carries a positive electric charge.
47. What is the charge of an electron?
An electron has a -1 charge.
48. Why is an electron negative?
It carries a negative electric charge.
49. What is the charge of a neutron?
A neutron has no charge.
50. Why is a neutron neutral?
It lacks an electric charge.
51. What is the mass of a proton?
A proton’s mass is about 1 amu.
52. Why is a proton heavier than an electron?
Protons have more mass than electrons.
53. What is the mass of an electron?
An electron’s mass is nearly zero.
54. Why is an electron’s mass small?
It is much lighter than nucleons.
55. What is the mass of a neutron?
A neutron’s mass is about 1 amu.
56. Why is a neutron’s mass like a proton’s?
Both have similar masses in the nucleus.
57. What is an alpha particle?
An alpha particle is a helium nucleus.
58. Why did Rutherford use alpha particles?
They are heavy and positively charged.
59. What is the gold foil experiment?
It showed atoms have a dense nucleus.
60. Why did alpha particles scatter?
They hit the nucleus’s positive charge.
61. What did Thomson’s model lack?
It lacked a nucleus.
62. Why was Thomson’s model replaced?
It couldn’t explain scattering results.
63. What did Rutherford’s model introduce?
It introduced a central nucleus.
64. Why was Rutherford’s model limited?
It didn’t explain electron stability.
65. What did Bohr improve?
Bohr added fixed electron orbits.
66. Why is Bohr’s model useful?
It explains atomic stability.
67. How many electrons in hydrogen’s shell?
Hydrogen has 1 electron.
68. Why does hydrogen have one valence electron?
It has one electron in its shell.
69. How many electrons in helium’s shell?
Helium has 2 electrons.
70. Why is helium’s shell full?
Its K shell holds 2 electrons.
71. How many electrons in lithium’s shells?
Lithium has 2 in K, 1 in L.
72. Why does lithium have one valence electron?
Its outermost shell has 1 electron.
73. How many electrons in carbon’s shells?
Carbon has 2 in K, 4 in L.
74. Why does carbon have four valence electrons?
Its L shell has 4 electrons.
75. How many electrons in oxygen’s shells?
Oxygen has 2 in K, 6 in L.
76. Why does oxygen have six valence electrons?
Its L shell has 6 electrons.
77. How many electrons in sodium’s shells?
Sodium has 2 in K, 8 in L, 1 in M.
78. Why does sodium have one valence electron?
Its M shell has 1 electron.
79. How many electrons in neon’s shells?
Neon has 2 in K, 8 in L.
80. Why is neon unreactive?
Its valence shell is full.
81. What is hydrogen’s atomic number?
Hydrogen’s atomic number is 1.
82. Why is hydrogen’s atomic number 1?
It has one proton.
83. What is oxygen’s atomic number?
Oxygen’s atomic number is 8.
84. Why is oxygen’s atomic number 8?
It has eight protons.
85. What is sodium’s atomic number?
Sodium’s atomic number is 11.
86. Why is sodium’s atomic number 11?
It has eleven protons.
87. What is carbon-12’s mass number?
Carbon-12’s mass number is 12.
88. Why is carbon-12’s mass number 12?
It has six protons, six neutrons.
89. What is carbon-14’s mass number?
Carbon-14’s mass number is 14.
90. Why is carbon-14’s mass number 14?
It has six protons, eight neutrons.
91. What are valence electrons for nitrogen?
Nitrogen has 5 valence electrons.
92. Why does nitrogen have 5 valence electrons?
Its L shell has 5 electrons.
93. What are valence electrons for fluorine?
Fluorine has 7 valence electrons.
94. Why does fluorine have 7 valence electrons?
Its L shell has 7 electrons.
95. What is the atomic number of nitrogen?
Nitrogen’s atomic number is 7.
96. Why is nitrogen’s atomic number 7?
It has seven protons.
97. What is the atomic number of fluorine?
Fluorine’s atomic number is 9.
98. Why is fluorine’s atomic number 9?
It has nine protons.
99. What is the atomic number of chlorine?
Chlorine’s atomic number is 17.
100. Why is chlorine’s atomic number 17?
It has seventeen protons.
101. How many electrons in boron’s shells?
Boron has 2 in K, 3 in L.
102. Why does boron have 3 valence electrons?
Its L shell has 3 electrons.
103. How many electrons in aluminum’s shells?
Aluminum has 2 in K, 8 in L, 3 in M.
104. Why does aluminum have 3 valence electrons?
Its M shell has 3 electrons.
105. What is nitrogen-14’s mass number?
Nitrogen-14’s mass number is 14.
106. Why is nitrogen-14’s mass number 14?
It has seven protons, seven neutrons.
107. What is nitrogen-15’s mass number?
Nitrogen-15’s mass number is 15.
108. Why is nitrogen-15’s mass number 15?
It has seven protons, eight neutrons.
109. What is the atomic number of boron?
Boron’s atomic number is 5.
110. Why is boron’s atomic number 5?
It has five protons.
111. What is the atomic number of aluminum?
Aluminum’s atomic number is 13.
112. Why is aluminum’s atomic number 13?
It has thirteen protons.
113. How many electrons in sulfur’s shells?
Sulfur has 2 in K, 8 in L, 6 in M.
114. Why does sulfur have 6 valence electrons?
Its M shell has 6 electrons.
115. How many electrons in calcium’s shells?
Calcium has 2 in K, 8 in L, 8 in M, 2 in N.
116. Why does calcium have 2 valence electrons?
Its N shell has 2 electrons.
117. What is the atomic number of sulfur?
Sulfur’s atomic number is 16.
118. Why is sulfur’s atomic number 16?
It has sixteen protons.
119. What is the atomic number of calcium?
Calcium’s atomic number is 20.
120. Why is calcium’s atomic number 20?
It has twenty protons.
121. What is sulfur-32’s mass number?
Sulfur-32’s mass number is 32.
122. Why is sulfur-32’s mass number 32?
It has sixteen protons, sixteen neutrons.
123. What is sulfur-34’s mass number?
Sulfur-34’s mass number is 34.
124. Why is sulfur-34’s mass number 34?
It has sixteen protons, eighteen neutrons.
125. How many electrons in phosphorus’s shells?
Phosphorus has 2 in K, 8 in L, 5 in M.
126. Why does phosphorus have 5 valence electrons?
Its M shell has 5 electrons.
127. How many electrons in argon’s shells?
Argon has 2 in K, 8 in L, 8 in M.
128. Why is argon’s valence shell full?
Its M shell has 8 electrons.
129. What is the atomic number of phosphorus?
Phosphorus’s atomic number is 15.
130. Why is phosphorus’s atomic number 15?
It has fifteen protons.
131. What is phosphorus-31’s mass number?
Phosphorus-31’s mass number is 31.
132. Why is phosphorus-31’s mass number 31?
It has fifteen protons, sixteen neutrons.
133. How many electrons in beryllium’s shells?
Beryllium has 2 in K, 2 in L.
134. Why does beryllium have 2 valence electrons?
Its L shell has 2 electrons.
135. What is the atomic number of beryllium?
Beryllium’s atomic number is 4.
136. Why is beryllium’s atomic number 4?
It has four protons.
137. What is beryllium-9’s mass number?
Beryllium-9’s mass number is 9.
138. Why is beryllium-9’s mass number 9?
It has four protons, five neutrons.
139. How many electrons in silicon’s shells?
Silicon has 2 in K, 8 in L, 4 in M.
140. Why does silicon have 4 valence electrons?
Its M shell has 4 electrons.
141. What is the atomic number of silicon?
Silicon’s atomic number is 14.
142. Why is silicon’s atomic number 14?
It has fourteen protons.
143. What is silicon-28’s mass number?
Silicon-28’s mass number is 28.
144. Why is silicon-28’s mass number 28?
It has fourteen protons, fourteen neutrons.
145. How many electrons in magnesium’s shells?
Magnesium has 2 in K, 8 in L, 2 in M.
146. Why does magnesium have 2 valence electrons?
Its M shell has 2 electrons.
147. What is the atomic number of magnesium?
Magnesium’s atomic number is 12.
148. Why is magnesium’s atomic number 12?
It has twelve protons.
149. What is magnesium-24’s mass number?
Magnesium-24’s mass number is 24.
150. Why is magnesium-24’s mass number 24?
It has twelve protons, twelve neutrons.
151. How many electrons in chlorine’s shells?
Chlorine has 2 in K, 8 in L, 7 in M.
152. Why does chlorine have 7 valence electrons?
Its M shell has 7 electrons.
153. What is chlorine-35’s mass number?
Chlorine-35’s mass number is 35.
154. Why is chlorine-35’s mass number 35?
It has seventeen protons, eighteen neutrons.
155. What is chlorine-37’s mass number?
Chlorine-37’s mass number is 37.
156. Why is chlorine-37’s mass number 37?
It has seventeen protons, twenty neutrons.
157. How many electrons in potassium’s shells?
Potassium has 2 in K, 8 in L, 8 in M, 1 in N.
158. Why does potassium have 1 valence electron?
Its N shell has 1 electron.
159. What is potassium-39’s mass number?
Potassium-39’s mass number is 39.
160. Why is potassium-39’s mass number 39?
It has nineteen protons, twenty neutrons.
161. What is the atomic number of potassium?
Potassium’s atomic number is 19.
162. Why is potassium’s atomic number 19?
It has nineteen protons.
163. What is oxygen-16’s mass number?
Oxygen-16’s mass number is 16.
164. Why is oxygen-16’s mass number 16?
It has eight protons, eight neutrons.
165. What is oxygen-18’s mass number?
Oxygen-18’s mass number is 18.
166. Why is oxygen-18’s mass number 18?
It has eight protons, ten neutrons.
167. What is the atomic number of helium?
Helium’s atomic number is 2.
168. Why is helium’s atomic number 2?
It has two protons.
169. What is helium-4’s mass number?
Helium-4’s mass number is 4.
170. Why is helium-4’s mass number 4?
It has two protons, two neutrons.
171. What is the atomic number of neon?
Neon’s atomic number is 10.
172. Why is neon’s atomic number 10?
It has ten protons.
173. What is neon-20’s mass number?
Neon-20’s mass number is 20.
174. Why is neon-20’s mass number 20?
It has ten protons, ten neutrons.
175. What is the atomic number of argon?
Argon’s atomic number is 18.
176. Why is argon’s atomic number 18?
It has eighteen protons.
177. What is argon-40’s mass number?
Argon-40’s mass number is 40.
178. Why is argon-40’s mass number 40?
It has eighteen protons, twenty-two neutrons.
179. Why are isotopes chemically similar?
They have the same number of protons.
180. What is an example of an isotope?
Carbon-12 and carbon-14.
181. Why do isotopes have different masses?
They have different neutron counts.
182. What is an example of an isobar?
Argon-40 and calcium-40.
183. Why do isobars have different properties?
They have different proton numbers.
184. What did Thomson’s experiment use?
It used a cathode ray tube.
185. Why did Thomson discover electrons?
Cathode rays showed negative particles.
186. What did Rutherford’s experiment use?
It used alpha particles and gold foil.
187. Why did Rutherford find a nucleus?
Alpha particles scattered from a dense core.
188. What did Bohr’s model explain?
It explained electron stability.
189. Why do electrons not fall into the nucleus?
They orbit in fixed energy levels.
190. What is the maximum electrons in the L shell?
The L shell holds 8 electrons.
191. Why is the M shell larger than the K shell?
It can hold more electrons.
192. What is the atomic number of carbon?
Carbon’s atomic number is 6.
193. Why is carbon’s atomic number 6?
It has six protons.
194. How many valence electrons in sodium?
Sodium has 1 valence electron.
195. Why does sodium form positive ions?
It loses one valence electron.
196. How many valence electrons in oxygen?
Oxygen has 6 valence electrons.
197. Why does oxygen form negative ions?
It gains two electrons to complete its shell.
198. What is the atomic number of lithium?
Lithium’s atomic number is 3.
199. Why is lithium’s atomic number 3?
It has three protons.
200. What is lithium-7’s mass number?
Lithium-7’s mass number is 7.
201. Why is lithium-7’s mass number 7?
It has three protons, four neutrons.
202. How many electrons in fluorine’s shells?
Fluorine has 2 in K, 7 in L.
203. Why is fluorine reactive?
It needs one electron to fill its shell.
204. What is the atomic number of sodium?
205. Why is sodium’s atomic number 11?
206. What is sodium-23’s mass number?
Sodium-23’s mass number is 23.
207. Why is sodium-23’s mass number 23?
It has eleven protons, twelve neutrons.
208. How many electrons in neon’s shells?
209. Why is neon stable?
Its valence shell is complete.
210. What is the atomic number of magnesium?
211. Why is magnesium’s atomic number 12?
212. What is magnesium-25’s mass number?
Magnesium-25’s mass number is 25.
213. Why is magnesium-25’s mass number 25?
It has twelve protons, thirteen neutrons.
214. How many electrons in aluminum’s shells?
215. Why does aluminum have 3 valence electrons?
216. What is the atomic number of aluminum?
217. Why is aluminum’s atomic number 13?
218. What is aluminum-27’s mass number?
Aluminum-27’s mass number is 27.
219. Why is aluminum-27’s mass number 27?
It has thirteen protons, fourteen neutrons.
220. How many electrons in silicon’s shells?
221. Why does silicon form bonds?
It shares four valence electrons.
222. What is the atomic number of silicon?
223. Why is silicon’s atomic number 14?
224. What is silicon-29’s mass number?
Silicon-29’s mass number is 29.
225. Why is silicon-29’s mass number 29?
It has fourteen protons, fifteen neutrons.
226. How many electrons in phosphorus’s shells?
227. Why does phosphorus have 5 valence electrons?
228. What is the atomic number of phosphorus?
229. Why is phosphorus’s atomic number 15?
230. What is phosphorus-32’s mass number?
Phosphorus-32’s mass number is 32.
231. Why is phosphorus-32’s mass number 32?
It has fifteen protons, seventeen neutrons.
232. How many electrons in sulfur’s shells?
233. Why does sulfur have 6 valence electrons?
234. What is the atomic number of sulfur?
235. Why is sulfur’s atomic number 16?
236. What is sulfur-33’s mass number?
Sulfur-33’s mass number is 33.
237. Why is sulfur-33’s mass number 33?
It has sixteen protons, seventeen neutrons.
238. How many electrons in chlorine’s shells?
239. Why does chlorine have 7 valence electrons?
240. What is the atomic number of chlorine?
241. Why is chlorine’s atomic number 17?
242. What is chlorine-36’s mass number?
Chlorine-36’s mass number is 36.
243. Why is chlorine-36’s mass number 36?
It has seventeen protons, nineteen neutrons.
244. How many electrons in argon’s shells?
245. Why is argon unreactive?
246. What is the atomic number of argon?
247. Why is argon’s atomic number 18?
248. What is argon-38’s mass number?
Argon-38’s mass number is 38.
249. Why is argon-38’s mass number 38?
It has eighteen protons, twenty neutrons.
250. How many electrons in potassium’s shells?
251. Why does potassium have 1 valence electron?
252. What is the atomic number of potassium?
253. Why is potassium’s atomic number 19?
254. What is potassium-40’s mass number?
Potassium-40’s mass number is 40.
255. Why is potassium-40’s mass number 40?
It has nineteen protons, twenty-one neutrons.
256. How many electrons in calcium’s shells?
257. Why does calcium have 2 valence electrons?
258. What is the atomic number of calcium?
259. Why is calcium’s atomic number 20?
260. What is calcium-40’s mass number?
Calcium-40’s mass number is 40.
261. Why is calcium-40’s mass number 40?
It has twenty protons, twenty neutrons.
262. What is the atomic number of beryllium?
263. Why is beryllium’s atomic number 4?
264. What is beryllium-10’s mass number?
Beryllium-10’s mass number is 10.
265. Why is beryllium-10’s mass number 10?
It has four protons, six neutrons.
266. How many electrons in boron’s shells?
267. Why does boron have 3 valence electrons?
268. What is boron-10’s mass number?
Boron-10’s mass number is 10.
269. Why is boron-10’s mass number 10?
It has five protons, five neutrons.
270. What is boron-11’s mass number?
Boron-11’s mass number is 11.
271. Why is boron-11’s mass number 11?
It has five protons, six neutrons.
272. How many electrons in carbon’s shells?
273. Why does carbon have 4 valence electrons?
274. What is carbon-13’s mass number?
Carbon-13’s mass number is 13.
275. Why is carbon-13’s mass number 13?
It has six protons, seven neutrons.
276. How many electrons in nitrogen’s shells?
Nitrogen has 2 in K, 5 in L.
277. Why does nitrogen have 5 valence electrons?
278. What is nitrogen-16’s mass number?
Nitrogen-16’s mass number is 16.
279. Why is nitrogen-16’s mass number 16?
It has seven protons, nine neutrons.
280. How many electrons in oxygen’s shells?
281. Why does oxygen have 6 valence electrons?
282. What is oxygen-17’s mass number?
Oxygen-17’s mass number is 17.
283. Why is oxygen-17’s mass number 17?
It has eight protons, nine neutrons.
284. How many electrons in fluorine’s shells?
285. Why does fluorine have 7 valence electrons?
286. What is fluorine-19’s mass number?
Fluorine-19’s mass number is 19.
287. Why is fluorine-19’s mass number 19?
It has nine protons, ten neutrons.
288. How many electrons in neon’s shells?
289. Why is neon’s valence shell full?
Its L shell has 8 electrons.
290. What is neon-22’s mass number?
Neon-22’s mass number is 22.
291. Why is neon-22’s mass number 22?
It has ten protons, twelve neutrons.
292. How many electrons in sodium’s shells?
293. Why does sodium have 1 valence electron?
294. What is sodium-24’s mass number?
Sodium-24’s mass number is 24.
295. Why is sodium-24’s mass number 24?
It has eleven protons, thirteen neutrons.
296. How many electrons in magnesium’s shells?
297. Why does magnesium have 2 valence electrons?
298. What is magnesium-26’s mass number?
Magnesium-26’s mass number is 26.
299. Why is magnesium-26’s mass number 26?
It has twelve protons, fourteen neutrons.
300. How many electrons in aluminum’s shells?
301. Why does aluminum have 3 valence electrons?
302. What is aluminum-28’s mass number?
Aluminum-28’s mass number is 28.
303. Why is aluminum-28’s mass number 28?
It has thirteen protons, fifteen neutrons.
304. How many electrons in silicon’s shells?
305. Why does silicon have 4 valence electrons?
306. What is silicon-30’s mass number?
Silicon-30’s mass number is 30.
307. Why is silicon-30’s mass number 30?
It has fourteen protons, sixteen neutrons.
308. How many electrons in phosphorus’s shells?
309. Why does phosphorus have 5 valence electrons?
310. What is phosphorus-30’s mass number?
Phosphorus-30’s mass number is 30.
311. Why is phosphorus-30’s mass number 30?
It has fifteen protons, fifteen neutrons.
312. How many electrons in sulfur’s shells?
313. Why does sulfur have 6 valence electrons?
314. What is sulfur-35’s mass number?
Sulfur-35’s mass number is 35.
315. Why is sulfur-35’s mass number 35?
It has sixteen protons, nineteen neutrons.
316. How many electrons in chlorine’s shells?
317. Why does chlorine have 7 valence electrons?
318. What is chlorine-38’s mass number?
Chlorine-38’s mass number is 38.
319. Why is chlorine-38’s mass number 38?
It has seventeen protons, twenty-one neutrons.
320. How many electrons in argon’s shells?
321. Why is argon’s valence shell full?
322. What is argon-36’s mass number?
Argon-36’s mass number is 36.
323. Why is argon-36’s mass number 36?
It has eighteen protons, eighteen neutrons.
324. How many electrons in potassium’s shells?
325. Why does potassium have 1 valence electron?
326. What is potassium-41’s mass number?
Potassium-41’s mass number is 41.
327. Why is potassium-41’s mass number 41?
It has nineteen protons, twenty-two neutrons.
328. How many electrons in calcium’s shells?
329. Why does calcium have 2 valence electrons?
330. What is calcium-42’s mass number?
Calcium-42’s mass number is 42.
331. Why is calcium-42’s mass number 42?
It has twenty protons, twenty-two neutrons.
332. What is the atomic number of hydrogen?
333. Why is hydrogen’s atomic number 1?
334. What is hydrogen-1’s mass number?
Hydrogen-1’s mass number is 1.
335. Why is hydrogen-1’s mass number 1?
It has one proton, no neutrons.
336. What is hydrogen-2’s mass number?
Hydrogen-2’s mass number is 2.
337. Why is hydrogen-2’s mass number 2?
It has one proton, one neutron.
338. What is the atomic number of helium?
339. Why is helium’s atomic number 2?
340. What is helium-3’s mass number?
Helium-3’s mass number is 3.
341. Why is helium-3’s mass number 3?
It has two protons, one neutron.
342. What is the atomic number of lithium?
343. Why is lithium’s atomic number 3?
344. What is lithium-6’s mass number?
Lithium-6’s mass number is 6.
345. Why is lithium-6’s mass number 6?
It has three protons, three neutrons.
346. What is the atomic number of beryllium?
347. Why is beryllium’s atomic number 4?
348. What is beryllium-8’s mass number?
Beryllium-8’s mass number is 8.
349. Why is beryllium-8’s mass number 8?
It has four protons, four neutrons.
350. What is the atomic number of boron?
351. Why is boron’s atomic number 5?
352. What is boron-12’s mass number?
Boron-12’s mass number is 12.
353. Why is boron-12’s mass number 12?
It has five protons, seven neutrons.
354. What is the atomic number of carbon?
355. Why is carbon’s atomic number 6?
356. What is carbon-11’s mass number?
Carbon-11’s mass number is 11.
357. Why is carbon-11’s mass number 11?
It has six protons, five neutrons.
358. What is the atomic number of nitrogen?
359. Why is nitrogen’s atomic number 7?
360. What is nitrogen-13’s mass number?
Nitrogen-13’s mass number is 13.
361. Why is nitrogen-13’s mass number 13?
It has seven protons, six neutrons.
362. What is the atomic number of oxygen?
363. Why is oxygen’s atomic number 8?
364. What is oxygen-15’s mass number?
Oxygen-15’s mass number is 15.
365. Why is oxygen-15’s mass number 15?
It has eight protons, seven neutrons.
366. What is the atomic number of fluorine?
367. Why is fluorine’s atomic number 9?
368. What is fluorine-18’s mass number?
Fluorine-18’s mass number is 18.
369. Why is fluorine-18’s mass number 18?
It has nine protons, nine neutrons.
370. What is the atomic number of neon?
371. Why is neon’s atomic number 10?
372. What is neon-21’s mass number?
Neon-21’s mass number is 21.
373. Why is neon-21’s mass number 21?
It has ten protons, eleven neutrons.
374. What is the atomic number of sodium?
375. Why is sodium’s atomic number 11?
376. What is sodium-22’s mass number?
Sodium-22’s mass number is 22.
377. Why is sodium-22’s mass number 22?
It has eleven protons, eleven neutrons.
378. What is the atomic number of magnesium?
379. Why is magnesium’s atomic number 12?
380. What is magnesium-27’s mass number?
Magnesium-27’s mass number is 27.
381. Why is magnesium-27’s mass number 27?
It has twelve protons, fifteen neutrons.
382. What is the atomic number of aluminum?
383. Why is aluminum’s atomic number 13?
384. What is aluminum-26’s mass number?
Aluminum-26’s mass number is 26.
385. Why is aluminum-26’s mass number 26?
It has thirteen protons, thirteen neutrons.
386. What is the atomic number of silicon?
387. Why is silicon’s atomic number 14?
388. What is silicon-27’s mass number?
Silicon-27’s mass number is 27.
389. Why is silicon-27’s mass number 27?
It has fourteen protons, thirteen neutrons.
390. What is the atomic number of phosphorus?
391. Why is phosphorus’s atomic number 15?
392. What is phosphorus-29’s mass number?
Phosphorus-29’s mass number is 29.
393. Why is phosphorus-29’s mass number 29?
It has fifteen protons, fourteen neutrons.
394. What is the atomic number of sulfur?
395. Why is sulfur’s atomic number 16?
396. What is sulfur-31’s mass number?
Sulfur-31’s mass number is 31.
397. Why is sulfur-31’s mass number 31?
It has sixteen protons, fifteen neutrons.
398. What is the atomic number of chlorine?
399. Why is chlorine’s atomic number 17?
400. What is chlorine-34’s mass number?
Chlorine-34’s mass number is 34.
401. Why is chlorine-34’s mass number 34?
It has seventeen protons, seventeen neutrons.
402. What is the atomic number of argon?
403. Why is argon’s atomic number 18?
404. What is argon-39’s mass number?
Argon-39’s mass number is 39.
405. Why is argon-39’s mass number 39?
It has eighteen protons, twenty-one neutrons.
406. What is the atomic number of potassium?
407. Why is potassium’s atomic number 19?
408. What is potassium-38’s mass number?
Potassium-38’s mass number is 38.
409. Why is potassium-38’s mass number 38?
It has nineteen protons, nineteen neutrons.
410. What is the atomic number of calcium?
411. Why is calcium’s atomic number 20?
412. What is calcium-44’s mass number?
Calcium-44’s mass number is 44.
413. Why is calcium-44’s mass number 44?
It has twenty protons, twenty-four neutrons.
414. Why are noble gases stable?
Their valence shells are full.
415. What is the valence shell of helium?
Helium’s valence shell is the K shell.
416. Why is helium unreactive?
Its K shell is fully filled.
417. What is the valence shell of neon?
Neon’s valence shell is the L shell.
418. Why is neon unreactive?
Its L shell is fully filled.
419. What is the valence shell of argon?
Argon’s valence shell is the M shell.
420. Why is argon unreactive?
Its M shell is fully filled.
421. Why do atoms bond?
To achieve a full valence shell.
422. What is the role of valence electrons?
They participate in chemical bonding.
423. Why is the nucleus small?
It contains only protons and neutrons.
424. Why is the atom mostly empty?
Electrons orbit far from the nucleus.
425. What is the charge of the nucleus?
The nucleus is positively charged.
426. Why do protons stay in the nucleus?
Nuclear forces hold them together.
427. What is the 2n² rule?
It gives the maximum electrons in a shell.
428. Why is the K shell limited to 2 electrons?
429. Why can the L shell hold 8 electrons?
430. Why can the M shell hold 18 electrons?
431. What is an atomic model?
It’s a representation of an atom’s structure.
432. Why did atomic models evolve?
New experiments revealed more details.
433. What did Thomson’s model show?
Electrons in a positive sphere.
434. What did Rutherford’s model show?
A nucleus with orbiting electrons.
435. What did Bohr’s model show?
Electrons in fixed orbits.
436. Why was Thomson’s model simple?
It assumed uniform positive charge.
437. Why was Rutherford’s model advanced?
It introduced a dense nucleus.
438. Why was Bohr’s model accepted?
439. What is the mass of hydrogen-1?
440. Why is hydrogen-1 called protium?
441. What is the mass of hydrogen-2?
442. Why is hydrogen-2 called deuterium?
443. What is the mass of hydrogen-3?
Hydrogen-3’s mass number is 3.
444. Why is hydrogen-3 called tritium?
It has one proton, two neutrons.
445. Why are hydrogen isotopes different?
446. What is the atomic number of all hydrogen isotopes?
All have atomic number 1.
447. Why do isotopes have the same atomic number?
They have the same proton count.
448. What is the atomic number of carbon isotopes?
All carbon isotopes have atomic number 6.
449. Why do carbon isotopes differ?
They have different neutron numbers.
450. What is the atomic number of oxygen isotopes?
All oxygen isotopes have atomic number 8.
451. Why do oxygen isotopes differ?
452. What is the atomic number of chlorine isotopes?
All chlorine isotopes have atomic number 17.
453. Why do chlorine isotopes differ?
454. What is the atomic number of sulfur isotopes?
All sulfur isotopes have atomic number 16.
455. Why do sulfur isotopes differ?
456. What is the atomic number of neon isotopes?
All neon isotopes have atomic number 10.
457. Why do neon isotopes differ?
458. What is the atomic number of argon isotopes?
All argon isotopes have atomic number 18.
459. Why do argon isotopes differ?
460. What is the atomic number of potassium isotopes?
All potassium isotopes have atomic number 19.
461. Why do potassium isotopes differ?
462. What is the atomic number of calcium isotopes?
All calcium isotopes have atomic number 20.
463. Why do calcium isotopes differ?
464. Why are isobars not isotopes?
Isobars have different proton numbers.
465. What is an example of hydrogen isotopes?
Protium, deuterium, tritium.
466. Why are protium and deuterium isotopes?
Same protons, different neutrons.
467. What is the mass number of protium?
Protium’s mass number is 1.
468. What is the mass number of deuterium?
Deuterium’s mass number is 2.
469. What is the mass number of tritium?
Tritium’s mass number is 3.
470. Why do atoms have isotopes?
Neutron numbers can vary.
471. What is the atomic number of tritium?
Tritium’s atomic number is 1.
472. Why is tritium’s atomic number 1?
473. What is the atomic number of deuterium?
Deuterium’s atomic number is 1.
474. Why is deuterium’s atomic number 1?
475. What is the atomic number of protium?
Protium’s atomic number is 1.
476. Why is protium’s atomic number 1?
477. Why do electrons orbit in shells?
Shells have specific energy levels.
478. What is the role of the nucleus?
It holds protons and neutrons.
479. Why is the nucleus heavy?
Protons and neutrons have mass.
480. What is the size of an atom?
An atom is about 10⁻¹⁰ meters.
481. Why is the nucleus tiny?
It’s much smaller than the atom.
482. What did Chadwick’s experiment show?
It showed neutral particles in the nucleus.
483. Why are neutrons important?
They contribute to atomic mass.
484. What is the charge of an atom?
An atom is electrically neutral.
485. Why do protons and electrons balance?
Their charges cancel each other.
486. What is the mass of an atom?
It’s mostly in the nucleus.
487. Why do electrons have little mass?
They are much lighter than nucleons.
488. What is the atomic number of fluorine?
489. Why is fluorine’s atomic number 9?
490. What is fluorine-20’s mass number?
Fluorine-20’s mass number is 20.
491. Why is fluorine-20’s mass number 20?
It has nine protons, eleven neutrons.
492. What is the atomic number of magnesium?
493. Why is magnesium’s atomic number 12?
494. What is magnesium-28’s mass number?
Magnesium-28’s mass number is 28.
495. Why is magnesium-28’s mass number 28?
It has twelve protons, sixteen neutrons.
496. What is the atomic number of silicon?
497. Why is silicon’s atomic number 14?
498. What is silicon-31’s mass number?
Silicon-31’s mass number is 31.
499. Why is silicon-31’s mass number 31?
It has fourteen protons, seventeen neutrons.
500. What is the atomic number of phosphorus?
501. Why is phosphorus’s atomic number 15?
502. What is phosphorus-33’s mass number?
Phosphorus-33’s mass number is 33.
503. Why is phosphorus-33’s mass number 33?
It has fifteen protons, eighteen neutrons.
Share this protal to share friends and complete unlimited tests here. You can also make friends on our protal also start mutual competition tests with your firends easily.