1,001 Chemistry Practice Problems For Dummies (2014)

Chapter 4. The Atom and Nuclear Chemistry

An atom consists of a nucleus surrounded by one or more electrons. Although the number of protons identifies the element, the electrons are the key to the chemistry. The arrangement of electrons in an atom influences the atom’s ability to gain, lose, or share electrons and therefore form compounds. Quantum numbers describe the arrangement of the electrons. Unstable atoms undergo nuclear decay to transform to stable atoms. Atoms may be broken apart by fission or joined by fusion.

The Problems You’ll Work On

In this chapter, you work with atoms and nuclear chemistry in the following ways:

Counting subatomic particles

Interpreting isotope notation

Writing electron configurations

Calculating average atomic mass and percent abundance

Understanding nuclear decay and balancing nuclear equations

Note: For access to the periodic table, see the Appendix.

What to Watch Out For

Remember the following when working on atoms and nuclear chemistry:

Note that unlike the atomic mass, the mass number is usually not found on the periodic table.

Remember the maximum number of electrons possible in each subshell, and follow Hund’s rule and the Aufbau principle when filling orbitals. Know the rules for assigning the four quantum numbers.

Know the common nuclear decay modes.

Remember that balancing nuclear equations depends on both the mass numbers and the atomic numbers.

Know how to calculate the half-life and how to use it.

Isotopes and Subatomic ­Particles

191–219 Answer the question on isotopes and subatomic particles.

191. How many protons are in an atom of sodium?

192. How many electrons are in an atom of bromine?

193. How many electrons are in an atom of nickel?

194. How many protons are in an atom of radon?

195. How many neutrons are in an atom of isotope potassium-40?

196. How is the atomic number related to the number of protons in an atom?

197. How is the mass number of an atom related to the number of neutrons?

198. How many protons, electrons, and neutrons are in an atom of isotope copper-63?

199. An atom has a mass number of 14 and 6 electrons. How many protons and neutrons does it have?

200. An atom has 40 electrons and 51 neutrons. What is its mass number, and how many protons does it have?

201. What does the top number in isotope notation represent?

202. What does the bottom number in isotope notation represent?

203. How many protons and neutrons are in ?

204. How many protons and neutrons are in ?

205. What is the isotope notation for an atom of carbon-12?

206. What is the isotope notation for an atom of chlorine-37?

207. What is the name of ?

208. How does an ion differ from an atom of the same element with regard to the numbers of subatomic particles?

209. When two atoms or ions have the same number of electrons, they’re said to be __________.

210. When an ion has a positive charge, how do the numbers of subatomic particles differ?

211. When an ion has a negative charge, how do the numbers of subatomic particles differ?

212. How many protons and electrons does have?

213. How many protons and electrons does have?

214. How many protons and electrons does have?

215. How many protons and electrons does have?

216. What is the isotope notation for an ion of silver-109 with a charge of positive 1?

217. What is the isotope notation for an ion of sulfur-34 with a charge of negative 2?

218. How many protons, neutrons, and electrons are in ?

219. How many protons, neutrons, and electrons are in ?

Electrons and Quantum ­Mechanics

220–234 Answer the questions on electrons and quantum mechanics.

220. What is the name of the premise that one electron fills each orbital in a subshell until all orbitals contain one electron and then electrons are added to fill in the second available spot in the subshell?

221. What rule or principle describes the order in which electrons fill orbitals?

222. What is the maximum number of electrons that can be in the f orbitals?

223. What is the maximum number of electrons that can be in the p orbitals?

224. What is the electron configuration of carbon?

225. What is the electron configuration of magnesium?

226. What is the electron configuration of argon?

227. What is the electron configuration of bromine?

228. What is the electron configuration of zirconium?

229. What is the expected electron configuration of plutonium?

230. Which quantum number describes the spin of the electron?

231. Which quantum number describes the average distance between the nucleus and the orbital?

232. Which quantum number describes how the various orbitals are oriented in space?

233. Which quantum number describes the shape of the orbital?

234. What are the possible values for the spin quantum number?

Average Atomic Mass

235–242 Answer the questions on average atomic mass.

235. The decimal numbers in the blocks of the periodic table represent the __________.

236. What is the average atomic mass of lithium that is 7.59% lithium-6 (mass of 6.0151 amu) and 92.41% lithium-7 (mass of 7.0160 amu)?

237. What is the average atomic mass of chlorine that is 75.78% chlorine-35 (mass of 34.96885 amu) and 24.22% chlorine-37 (mass of 36.9659 amu)?

238. What is the average atomic mass of magnesium, given the information in the following table?

239. What is the average atomic mass of potassium, given the information in the following table?

240. What is the average atomic mass of iron, given the information in the following table?

241. What is the average atomic mass of krypton, given the information in the following table?

242. If the average atomic mass of boron is 10.81 amu, what is the percent abundance of boron-11 (mass of 11.009306 amu) if the only other isotope is boron-10 (mass of 10.012937 amu)?

Nuclear Reactions and ­Nuclear Decay

243–252 Answer the question on aspects of nuclear reactions and nuclear decay.

243. What is the primary nuclear process that occurs in the sun?

244. In which nuclear process does a nucleus split into two or more smaller elements and possibly some extra neutrons?

245. What is it called when a helium nucleus is ejected from the nucleus of an atom during a nuclear reaction?

246. When a ray is a byproduct of a nuclear reaction, what nuclear process has occurred?

247. What is the isotope (nuclear) notation for a particle that is produced from beta decay?

248. A particle is a product of which nuclear reaction?

249. is an example of what type of nuclear reaction?

250. is an example of what type of nuclear reaction?

251. is an example of what type of nuclear reaction?

252. is an example of what type of nuclear reaction?

Completing Nuclear Reactions

253–260 Determine the missing part of the equation.

253.

254.

255.

256.

257.

258.

259.

260.

Half-Lives

261–270 Answer the question on half-lives.

261. After five half-lives, how many grams of a 400.-g radioactive sample remain undecayed?

262. After three half-lives, how many grams of a 50.0-g radioactive sample have decayed?

263. If 5.15 g of a radioactive sample remains undecayed after six half-lives, how many grams were in the original sample?

264. A radioactive sample starts with 1.500 × 10²⁰ undecayed atoms. When measured again at a later date, the sample has 9.375 × 10¹⁸ undecayed atoms. How many half-lives have passed?

265. What fraction of a sample remains undecayed after 39 hours if the half-life of the sample is 13 hours?

266. Iodine-131 has a half-life of 8.02 days. If the original sample contained 25.0 g of iodine-131, how many grams have decayed after 56.14 days?

267. Strontium-90 has a half-life of 28.9 years. How many grams were in the original sample if 11 g remain undecayed after 115.6 years?

268. In 5 minutes, a radioactive sample decays from 2.56 × 10¹⁰ atoms to 8.00 × 10⁸ atoms. How long is the isotope’s half-life?

269. What fraction of a sample has decayed after 320 days if the half-life of the sample is 160 days?

270. If a radioactive sample decays from 2.5 kg to 0.61 g and the isotope has a half-life of 9.35 hours, how much time has passed?