Chapter 2

What are the three fundamental particles from which atoms are built? What are their electric charges? Which of these particles constitute the nucleus of an atom? Which is the least massive particle of the three?

Define mass number. What is the difference between mass number and atomic mass?

A gold atom has a radius of \(145 \mathrm{pm} .\) If you could string gold atoms like beads on a thread, how many atoms would you need to have a necklace \(36 \mathrm{cm}\) long?

Give the complete symbol \(\left(^{A}_{Z} X\right),\) including atomic number and mass number, for each of the following atoms: (a) magnesium with 15 neutrons, (b) titanium with 26 neutrons, and (c) zinc with 32 neutrons.

Give the complete symbol \(\left(^{A}_{Z} X\right),\) including atomic number and mass number, of (a) a nickel atom with 31 neutrons, (b) a plutonium atom with 150 neutrons, and (c) a tungsten atom with 110 neutrons.

How many electrons, protons, and neutrons are there in each of the following atoms? (a) magnesium- \(24,^{24} \mathrm{Mg}\) (b) tin-119, \(^{119} \mathrm{Sn}\) (c) thorium- \(232,^{232}\) Th (d) carbon-13, \(^{13} \mathrm{C}\) (e) copper-63, \(^{63}\) Cu (f) bismuth- \(205,^{205} \mathrm{Bi}\)

Atomic structure. (a) The synthetic radioactive element technetium is used in many medical studies. Give the number of electrons, protons, and neutrons in an atom of technetium-99. (b) Radioactive americium- 241 is used in household smoke detectors and in bone mineral analysis. Give the number of electrons, protons, and neutrons in an atom of americium-241.

From cathode ray experiments, J. J. Thomson estimated that the mass of an electron was "about a thousandth" of the mass of a proton. How accurate is that estimate? Calculate the ratio of the mass of an electron to the mass of a proton.

In 1886 Eugene Goldstein observed positively charged particles moving in the opposite direction to electrons in a cathode ray tube (illustrated below). From their mass, he concluded that these particles were formed from residual gas in the tube. For example, if the cathode ray tube contained helium, the canal rays consisted of \(\mathrm{He}^{+}\) ions. Describe a process that could lead to these ions.

Marie Curie was born in Poland but studied and carried out her research in Paris. In \(1903,\) she shared the Nobel Prize in Physics with H. Becquerel and her husband Pierre for their discovery of radioactivity. (In 1911 she received the Nobel Prize in Chemistry for the discovery of two new chemical elements, radium and polonium, the latter named for her homeland, Poland.) They and others observed that a radioactive substance could emit three types of radiation: alpha \((\alpha),\) beta \((\beta)\) and gamma \((\gamma) .\) If the radiation from a radioactive source is passed between electrically charged plates, some particles are attached to the positive plate, some to the negative plate, and others feel no attraction. Which particles are positively charged, which are negatively charged, and which have no charge? Of the two charged particles, which has the most mass?

Early in the 1800 s John Dalton proposed that an atom was a "solid, massy, hard, impenetrable, moveable particle." Critique this description. How does this description misrepresent atomic structure?

The mass of an \(^{16} \mathrm{O}\) atom is \(15.995 \mathrm{u}\). What is its mass relative to the mass of an atom of \(^{12} \mathrm{C} ?\)

What is the mass of one \(^{16} \mathrm{O}\) atom, in grams? (The mass of an \(^{16} \mathrm{O} \text { atom is } 15.995 \text { u.}\))

Cobalt has three radioactive isotopes used in medical studies. Atoms of these isotopes have 30 \(31,\) and 33 neutrons, respectively. Give the complete symbol for each of these isotopes.

Naturally occurring silver exists as two isotopes having mass numbers 107 and 109. How many protons, neutrons, and electrons are there in each of these isotopes?

Name and describe the composition of the three hydrogen isotopes.

Which of the following are isotopes of element \(X\) the atomic number for which is \(9: ^{19}_{9} \mathrm{X},^{20}_{9} \mathrm{X},^{9} _{18} \mathrm{A}\) and \(^{21}_{9} \mathrm{X} ?\)

Thallium has two stable isotopes, \(^{203} \mathrm{Tl}\) and \(^{205} \mathrm{Tl}\). Knowing that the atomic weight of thallium is \(204.4,\) which isotope is the more abundant of the two?

Strontium has four stable isotopes. Strontium-84 has a very low natural abundance, but \(^{86} \mathrm{Sr},^{87} \mathrm{Sr}_{t}\) and \(^{88}\) Sr are all reasonably abundant. Knowing that the atomic weight of strontium is \(87.62,\) which of the more abundant isotopes predominates?

Verify that the atomic weight of lithium is 6.94 given the following information: \(^{6} \mathrm{Li},\) mass \(=6.015121 \mathrm{u} ;\) percent abundance\(=7.50 \%\) \(^{7} \mathrm{Li},\) mass \(=7.016003 \mathrm{u} ;\) percent abundance \(=92.50 \%\)

Verify that the atomic weight of magnesium is 24.31, given the following information: \(^{24} \mathrm{Mg},\) mass \(=23.985042 \mathrm{u} ;\) percent abundance \(=78.99 \%\) \(^{25} \mathrm{Mg},\) mass \(=24.985837 \mathrm{u} ;\) percent abundance \(=10.00 \%\) \(^{26} \mathrm{Mg},\) mass \(=25.982593 \mathrm{u} ;\) percent abundance \(=11.01 \%\)

Titanium and thallium have symbols that are easily confused with each other. Give the symbol, atomic number, atomic weight, and group and period number of each element. Are they metals, metalloids, or nonmetals?

How many periods of the periodic table have 8 elements, how many have 18 elements, and how many have 32 elements?

How many elements occur in the seventh period? What is the name given to the majority of these elements, and what well-known property characterizes them?

Select answers to the questions listed below from the following list of elements whose symbols start with the letter \(\mathrm{C}: \mathrm{C}, \mathrm{Ca}, \mathrm{Cr}, \mathrm{Co}, \mathrm{Cd}, \mathrm{Cl}, \mathrm{Cs}, \mathrm{Ce}\) \(\mathrm{Cm}, \mathrm{Cu},\) and Cf. (You should expect to use some symbols more than once.) (a) Which are nonmetals? (b) Which are main group elements? (c) Which are lanthanides? (d) Which are transition elements? (e) Which are actinides? (f) Which are gases?

Give the name and chemical symbol for the following. (a) a nonmetal in the second period (b) an alkali metal in the fifth period (c) the third-period halogen (d) an element that is a gas at \(20^{\circ} \mathrm{C}\) and 1 atmosphere pressure

Classify the following elements as metals, metalloids, or nonmetals: \(\mathrm{N}, \mathrm{Na}, \mathrm{Ni}, \mathrm{Ne},\) and \(\mathrm{Np}.\)

Here are symbols for five of the seven elements whose names begin with the letter \(\mathrm{B}: \mathrm{B}, \mathrm{Ba}, \mathrm{Bk}, \mathrm{Bi}\) and Br. Match each symbol with one of the descriptions below. (a) a radioactive element (b) a liquid at room temperature (c) a metalloid (d) an alkaline earth element (e) a group 5 A element

What is the charge on the common monatomic ions of the following elements? (a) magnesium (b) zinc (c) nickel (d) gallium

What is the charge on the common monatomic ions of the following elements? (a) selenium (b) fluorine (c) iron (d) nitrogen

Give the symbol, including the correct charge, for each of the following ions: (a) barium ion (b) titanium(IV) ion (c) phosphate ion (d) hydrogen carbonate ion (e) sulfide ion (f) perchlorate ion (g) cobalt(II) ion (h) sulfate ion

Give the symbol, including the correct charge, for each of the following ions: (a) permanganate ion (b) nitrite ion (c) dihydrogen phosphate ion (d) ammonium ion (e) phosphate ion (f) sulfite ion

When a potassium atom becomes a monatomic ion, how many electrons does it lose or gain? What noble gas atom has the same number of electrons as a potassium ion?

When oxygen and sulfur atoms become monatomic ions, how many electrons does each lose or gain? Which noble gas atom has the same number of electrons as an oxide ion? Which noble gas atom has the same number of electrons as a sulfide ion?

What are the charges on the ions in an ionic compound containing the elements barium and bromine? Write the formula for the compound.

What are the charges of the ions in an ionic compound containing cobalt(III) and fluoride ions? Write the formula for the compound.

Give the formula and the number of each ion that makes up each of the following compounds: (a) \(\mathrm{K}_{2} \mathrm{S}\) (b) \(\cos \mathrm{O}_{4}\) (c) \(\mathrm{KMnO}_{4}\) (d) \(\left(\mathrm{NH}_{4}\right)_{3} \mathrm{PO}_{4}\) (e) \(\mathrm{Ca}(\mathrm{ClO})_{2}\) (f) \(\mathrm{NaCH}_{3} \mathrm{CO}_{2}\)

Give the formula and the number of each ion that makes up each of the following compounds: (a) \(\mathrm{Mg}\left(\mathrm{CH}_{3} \mathrm{CO}_{2}\right)_{2}\) (d) \(\mathrm{Ti}\left(\mathrm{SO}_{4}\right)_{2}\) (b) \(\mathrm{Al}(\mathrm{OH})_{3}\) (e) \(\mathrm{KH}_{2} \mathrm{PO}_{4}\) (c) \(\mathrm{CuCO}_{3}\) (f) \(\mathrm{CaHPO}_{4}\)

Cobalt forms \(\mathrm{Co}^{2+}\) and \(\mathrm{Co}^{3+}\) ions. Write the formulas for the two cobalt oxides formed by these transition metal ions.

Platinum is a transition element and forms \(\mathrm{Pt}^{2+}\) and \(\mathrm{Pt}^{4+}\) ions. Write the formulas for the compounds of each of these ions with (a) chloride ions and (b) sulfide ions.

Which of the following are correct formulas for ionic compounds? For those that are not, give the correct formula. (a) \(\mathrm{AlCl}_{2}\) (b) \(\mathrm{KF}_{2}\) (c) \(\mathrm{Ga}_{2} \mathrm{O}_{3}\) (d) \(\mathrm{MgS}\)

Which of the following are correct formulas for ionic compounds? For those that are not, give the correct formula. (a) \(\mathrm{Ca}_{2} \mathrm{O}\) (b) \(\operatorname{SrBr}_{2}\) (c) \(\mathrm{Fe}_{2} \mathrm{O}_{5}\) (d) \(\mathrm{Li}_{2} \mathrm{O}\)

Name each of the following ionic compounds: (a) \(\mathrm{K}_{2} \mathrm{S}\) (b) \(\cos \mathrm{O}_{4}\) (c) \(\left(\mathrm{NH}_{4}\right)_{3} \mathrm{PO}_{4}\) (d) \(\mathrm{Ca}(\mathrm{ClO})_{2}\)

Name each of the following ionic compounds: (a) \(\mathrm{Ca}\left(\mathrm{CH}_{3} \mathrm{CO}_{2}\right)_{2}\) (b) \(\mathrm{Ni}_{3}\left(\mathrm{PO}_{4}\right)_{2}\) (c) \(\mathrm{Al}(\mathrm{OH})_{3}\) (d) \(\mathrm{KH}_{2} \mathrm{PO}_{4}\)

Give the formula for each of the following ionic compounds: (a) ammonium carbonate (b) calcium iodide (c) copper(II) bromide (d) aluminum phosphate (e) silver(I) acetate

Give the formula for each of the following ionic compounds: (a) calcium hydrogen carbonate (b) potassium permanganate (c) magnesium perchlorate (d) potassium hydrogen phosphate (e) sodium sulfite

Write the formulas for the four ionic compounds that can be made by combining each of the cations \(\mathrm{Na}^{+}\) and \(\mathrm{Ba}^{2+}\) with the anions \(\mathrm{CO}_{3}^{2-}\) and I-.. Name each of the compounds.

Write the formulas for the four ionic compounds that can be made by combining the cations \(\mathrm{Mg}^{2+}\) and \(\mathrm{Fe}^{3+}\) with the anions \(\mathrm{PO}_{4}^{3-}\) and \(\mathrm{NO}_{3}^{-} .\) Name each compound formed.

Sodium ions, \(\mathrm{Na}^{+}\), form ionic compounds with fluoride ions, \(\mathrm{F}^{-},\) and iodide ions, \(\mathrm{I}^{-}\). The radii of these ions are as follows: \(\mathrm{Na}^{+}=116 \mathrm{pm}\) \(\mathrm{F}^{-}=119 \mathrm{pm} ;\) and \(\mathrm{I}^{-}=206 \mathrm{pm} .\) In which ionic compound, NaF or NaI, are the forces of attraction between cation and anion stronger? Explain your answer.

Consider the two ionic compounds \(\mathrm{NaCl}\) and CaO. In which compound are the cation-anion attractive forces stronger? Explain your answer.