The Atom and Nuclear Chemistry

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

*The mass number is equal to the number of neutrons plus the atomic number (the number of protons).* The majority of the mass of the atom is in the nucleus, where you find the protons and neutrons, collectively called nucleons. By adding the number of neutrons to the atomic number (which equals the number of protons), you get the mass number.

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

-1/2, 1/2 An electron can spin in only two directions: clockwise or counterclockwise. Because direction is relative, each has a numeric value of 1/2 assigned to the electron; one direction is considered positive, and the other is negative.

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

11 protons The atomic number of an element is equal to the number of protons. Sodium, Na, is atomic number 11, so it has 11 protons.

204. How many protons and neutrons are in ²⁵₁₁ Na?

11 protons, 14 neutrons The bottom number in isotope notation is the atomic number, which is equal to the number of protons, so has 11 protons. The number of neutrons is equal to the mass number (the top number) minus the atomic number (the bottom number): 25 - 11 = 14 neutrons.

214. How many protons and electrons does have ³⁰₁₃Al³⁺?

13 protons and 10 electrons For an ion to be positive, the atom must have more protons than electrons. needs to have three more protons than electrons, because the charge is +3. With an atomic number of 13, the aluminum ion must have three fewer electrons than protons: 13 - 3 = 10 electrons.

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

14 There are seven f orbitals. Each orbital can hold a maximum of two electrons, so a maximum of fourteen electrons are in the f orbitals.

215. How many protons and electrons does have ³³P ³⁻?

15 protons and 18 electrons Sometimes you need to look up the atomic number to determine the number of protons. The atomic number of phosphorus, P, is 15, so phosphorus has 15 protons. You can find the number of electrons by subtracting the charge from the number of protons: 15 - (-3) = 15 + 3 = 18 electrons.

224. What is the electron configuration of carbon?

1s²2s²2p² Carbon, C, has an atomic number of 6, which means that it has six protons and six electrons. Electrons fill orbitals from lowest energy to highest energy, so the first energy level gets filled before the second energy level. Remember that the s orbital can hold a maximum of two electrons and that the p orbitals can hold a maximum of six electrons. To check the electron configuration, note that adding the superscripts on 1s²2s²2p² gives you 2 + 2 + 2 = 6 electrons.

225. What is the electron configuration of magnesium?

1s²2s²2p⁶3s² Magnesium, Mg, has an atomic number of 12, so it has 12 protons and 12 electrons. Electrons fill orbitals from the first energy level up to the third in magnesium. The first energy level contains two electrons, the second energy level contains eight electrons (two in an s orbital and six in a p orbital), and the third energy level contains the last two electrons, for a total of 12 electrons.

226. What is the electron configuration of argon?

1s²2s²2p⁶3s²3p⁶ Argon, Ar, has an atomic number of 18, so it has 18 protons and 18 electrons. The electrons fill the first and second energy levels completely (two in each s orbital and six in the p orbital). The remaining electrons fill the 3s and 3p orbitals.

227. What is the electron configuration of bromine?

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁵ An atom of bromine, Br, has 35 protons and 35 electrons. The first energy level can hold a maximum of two electrons, and the second energy level can hold a maximum of eight electrons (two in the s orbital and six in the p orbital). The third energy level can hold a maximum of 18 electrons (two in an s orbital, six in p orbitals, and 10 in d orbitals), and the fourth energy level contains the remainder of the electrons. Remember that the 4s orbital doesn't require as much energy as the 3d orbital in order to fill with electrons, so the 4s orbital fills first.

228. What is the electron configuration of zirconium?

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d² An atom of zirconium, Zr, has 40 protons and 40 electrons. The first energy level contains two electrons, the second energy level contains eight electrons (two in the s orbital and six in the p orbital), the third energy level contains 18 electrons, and the fourth energy level contains the remainder of the electrons. Remember that the 5s orbital doesn't require as much energy as the 4d orbital in order to fill with electrons, so the 5s orbital fills first.

229. What is the expected electron configuration of plutonium?

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p⁶7s²5f⁶ Finding the expected electron configuration of plutonium, Pu, is hard because there are so many electrons. When you get down to the bottom of the periodic table, electrons are in every energy level. Just be sure to add them in the correct order based on the energy it takes to fill the orbitals. Adding the superscripts in the expected electron configuration, 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p⁶7s²5f⁶ , gives you 2 + 2 + 6 + 2 + 6 + 2 + 10 + 6 + 2 + 10 + 6 + 2 + 14 + 10 + 6 + 2 + 6 = 94 electrons.

212. How many protons and electrons does have ⁴⁰₂₀C²⁺?

20 protons and 18 electrons ⁴⁰₂₀C²⁺ has a positive charge, so the number of protons must be greater than the number of electrons. The atomic number of Ca is 20 (the bottom number in isotope notation), giving you 20 protons. To find the number of electrons, simply subtract the charge from the number of protons: 20 - 2 = 18 electrons.

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

21 neutrons To find the number of neutrons in an atom, subtract the atomic number (which equals the number of protons) from the atom's mass number (which equals the number of protons + the number of neutrons). Here are the calculations for potassium-40: # of neutrons = mass number 40 -19 protons = 21 neutrons

218. How many protons, neutrons, and electrons are in ⁵²Cr ⁶⁺

24 protons, 28 neutrons, 18 electrons Chromium, Cr, has an atomic number of 24, which is equal to the number of protons. If the mass number is 52, then the atom contains 28 neutrons, because the mass number minus the atomic number (from the periodic table) gives you the number of neutrons: 52 - 24 = 28 neutrons. To get the number of electrons, subtract the ion's charge from the number of protons: 24 - 6 = 18 electrons. This answer makes sense because a +6 charge means that there are six more protons than electrons.

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

28 electrons Nickel, Ni, has 28 protons. Because the number of protons equals the number of electrons in an atom, an atom of nickel contains 28 electrons.

219. How many protons, neutrons, and electrons are in ⁶²Ni ³⁺

28 protons, 34 neutrons, 25 electrons Nickel, Ni, has an atomic number of 28, which is equal to the number of protons. Because the top number in the isotope notation is 62, the mass number is 62. To find the number of neutrons, subtract the atomic number (from the periodic table) from the mass number: 62 - 28 = 34 neutrons. To get the number of electrons, subtract the ion's charge from the number of protons: 28 - 3 = 25 electrons. This answer makes sense because a +3 charge means that there are three more protons than electrons.

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

29 protons, 29 electrons, and 34 neutrons The number of protons is equal to the atomic number; therefore, copper, Cu, has 29 protons. Because the atom is neutral, the number of protons equals the number of electrons. To get the number of neutrons, subtract the number of protons (29) from the mass number. The mass number, 63, follows the name of the element in copper-63, so the number of neutrons is 63 - 29 = 34.

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

35 electrons The number of protons is equal to the number of electrons in an atom, which is neutral. Bromine, Br, is atomic number 35. It has 35 protons, so it has 35 electrons.

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)?

35.45 amu You have two isotopes, so take the percent of each isotope, multiply it by the given mass of the isotope, and then add the two numbers together: 75.78/100 x34.96885 amu =26.49939 amu 24.22/100 x 36.9659 amu =8.95314 amu 26.49939 amu +8.95314 amu =35.45253 amu 35.45 amu

213. How many protons and electrons does have ¹³¹₅₃I¹⁻?

53 protons and 54 electrons For an ion to be negative, it needs to have more electrons than protons. Iodine has an atomic number of 53, so it has 53 protons. Because the iodine ion has a -1 charge, the ion must have one more electron than proton, giving you a total of 54 electrons.

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

6 There are three p orbitals. Each orbital can hold a maximum of two electrons, so a maximum of six electrons are in the p orbitals.

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

6 protons and 8 neutrons If the atom has 6 electrons, then it has 6 protons, because the positive and negative charges have to cancel each other out. The number of neutrons is equal to the mass number minus the number of protons: 14 - 6 = 8.

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)?

6.940 amu To find the average atomic mass, take the percent abundance and multiply it by the given mass of the element. Repeat for as many isotopes as are given. Then add the multiplied numbers together: 7.59/100 x 6.0151 amu =0.45655 amu 92.41/100 x 7.0160 amu = +6.48349 amu 0.45655 amu +6.48349 amu =6.94004 6.940 amu

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)?

80.% boron-11 To solve this problem, you need to rely on your algebra skills. You have two isotopes of boron, and you have to solve for the percent abundance of one of the isotopes. So here's your initial equation: (% B-11)(mass B-11) + (% B-10)(mass B-10) = average atomic massNext, substitute in the given numbers from the problem: (% B-11)(11.009306 amu) + (% B-10)(10.012397 amu) = 10.81 amu You have two unknown percentages, and you need to figure out how they're related. The two percentages have to add up to 100%: (% B-11) + (% B-10) = 100%. In decimal form, 100% equals 1, so if you consider the amount of boron-11 to be x, then the amount of boron-10 has to be 1 - x. By substituting these values into the initial equation and solving for x, you can find the percent of boron-11: The subtraction in the fourth line (10.81 - 10.012937) limits the answer to two decimal places (two significant figures), which in turn limits the final answer to two significant figures.

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

86 protons The number of protons in an atom is equal to the element's atomic number. Radon, Rn, is atomic number 86, so it has 86 protons.

203. How many protons and neutrons are in ¹⁸₉F?

9 protons, 9 neutrons In isotope notation, the bottom number is equal to the number of protons, so has nine protons. The number of neutrons is equal to the top number (mass number) minus the bottom number (atomic number): 18 - 9 = 9 neutrons.

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

An ion has a different number of electrons from the atom. An ion is an atom that has either gained or lost electrons. If, instead, the number of protons changes, then the element's identity is changed (transmutation). If the number of neutrons changes, you have an isotope.

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

Aufbau principle The Aufbau principle describes the order in which electrons fill orbitals.

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?

Hund's rule "Electrons fill subshells singly before doubly" is a shortened restatement of Hund's rule.

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

The atomic number is equal to the number of protons. The general definition of atomic number is the number of protons in an atom.

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

The number of protons is greater than the number of electrons. Protons are positive and electrons are negative, so for an ion to be positive, it needs more protons than electrons. An ion with a positive charge has lost electrons.

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

The number of protons is less than the number of electrons. For an ion to have a negative charge, it must have more electrons than protons. An ion with a negative charge has gained electrons.

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

To write the isotope notation, start with the symbol for silver, Ag. To the left of the symbol and slightly above the base line, write 109, the mass number that follows the hyphen after the element's name. Then write the atomic number, 47 (from the periodic table), below 109. Write a plus sign as the superscript after the Ag to indicate the charge; writing the 1 isn't necessary because it's understood.

207. What is the name of Ar ?

argon-35 Ar is the symbol for argon. When you write the isotope name, the top number in isotope notation (the mass number) becomes the number that follows a hyphen and the element's name: argon-35.

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

average atomic mass The decimal number found in most blocks on the periodic table is the weighted average of the relative abundance of all known isotopes. The more common an isotope is, the more it affects the average atomic mass.

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

isoelectronic The prefix for same is iso-, so two atoms or ions with the same number of electrons are said to be isoelectronic.

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

mass number 91, 40 protons The number of protons equals the number of electrons in an atom, so 40 electrons means 40 protons. The element is atomic number 40, zirconium (Zr). The mass number is equal to the number of protons plus the number of neutrons. The atom contains 51 neutrons, so the mass number is 40p + 51n = 91.

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

the angular momentum quantum number The angular momentum quantum number, l, describes the shape of the orbital.

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

the magnetic quantum number The magnetic quantum number, ml, describes how the orbitals are oriented in threedimensional space.

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

the mass number In isotope notation ⁰X, the top number o represents the mass number, which is the sum of the number of protons and neutrons in the nucleus of the atom.

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

the number of protons In isotope notation ₀X, the bottom number o represents the atomic number, which is the same as the number of protons in the nucleus of the atom.

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

the principal quantum number The principal quantum number, n, describes the average distance between the nucleus and the orbital, with the first energy level at a distance of 1.

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

the spin quantum number The spin quantum number, s, describes the direction of the spin of the electron. According to this model, the electron spins either clockwise or counterclockwise.

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

³⁴₁₆S²⁻ The symbol for sulfur is S. Write the mass number, 34, to the upper left of the S. Sulfur has an atomic number of 16, so write 16 under the 34. Represent the charge of negative 2 by writing the superscript 2- after the S.

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

³⁷₁₇Cl In isotope notation, chlorine-37 has the atomic symbol Cl with a mass number of 37 on top. The bottom number is the atomic number of chlorine, 17. The mass number follows the name of the element in the isotope name (chlorine-37), and you can find the element's symbol and atomic number on the periodic table.

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

¹²₆C In isotope notation, carbon-12 has the atomic symbol C with a mass number of 12 on top. The bottom number is the atomic number of carbon, 6. The mass number follows the name of the element in the isotope name (carbon-12), and you can find the element's symbol and atomic number on the periodic table.