Chapter 2

On what basis did Mendeleev construct his periodic table? On what basis are the elements arranged in the modern periodic table?

Using their positions in the periodic table, explain why is it not surprising that strontium-90, a radioactive isotope, replaces calcium in newly formed bones.

Why would you reasonably expect cadmium to be a contaminant in zinc but not in silver?????

Using the symbol for nitrogen, \({ }_{7}^{14} \mathrm{~N}_{2}^{0},\) indicate what information is conveyed by the two superscripts, and what information is conveyed by the two subscripts.

Make a rough sketch of the periodic table and mark off those areas where you would find (a) the representative elements, (b) the transition elements, and (c) the inner transition elements.

Which of the following is (a) an alkali metal? Ca, \(\mathrm{Cu}\), In, \(\mathrm{Li}, \mathrm{S}\) (b) a halogen? Ce, \(\mathrm{Hg}, \mathrm{Si}, \mathrm{O}, \mathrm{I}\) (c) a transition element? \(\mathrm{Pb}, \mathrm{W}, \mathrm{Ca}, \mathrm{Cs}, \mathrm{P}\) (d) a noble gas? \(\mathrm{Xe}, \mathrm{Se}, \mathrm{H}, \mathrm{Sr}, \mathrm{Zr}\) (e) a lanthanide element? \(\mathrm{Th}, \mathrm{Sm}, \mathrm{Ba}, \mathrm{F}, \mathrm{Sb}\) (f) an actinide element? Ho, \(\mathrm{Mn}, \mathrm{Pu},\) At, \(\mathrm{Na}\) (g) an alkaline earth metal? \(\mathrm{Mg}, \mathrm{Fe}, \mathrm{K}, \mathrm{Cl}, \mathrm{Ni}\)

Name five physical properties that we usually observe for metals.

Which physical property of metalloids distinguishes them from metals and nonmetals?

Most periodic tables have a heavy line that looks like a staircase starting from boron down to polonium. What information does this line convey?

What is the difference between an atom and a molecule?

What do we mean when we say a chemical equation is balanced? Why do we balance chemical equations?

For a chemical reaction, what do we mean by the term reactants? What do we mean by the term products?

The combustion of a thin wire of magnesium metal (Mg) in an atmosphere of pure oxygen produces the brilliant light of a flashbulb, once commonly used in photography. After the reaction, a thin film of magnesium oxide is seen on the inside of the bulb. The equation for the reaction is $$ 2 \mathrm{Mg}+\mathrm{O}_{2} \longrightarrow 2 \mathrm{MgO} $$ (a) State in words how this equation is read. (b) Give the formula(s) of the reactants. (c) Give the formula(s) of the products.

Describe what kind of event must occur (involving electrons) if the atoms of two different elements are to react to form an ionic compound.

With what kind of elements do metals react?

What is an ion? How does it differ from an atom or a molecule?

Why do we use the term formula unit for ionic compounds instead of the term molecule? Can we use that term for molecules, atoms, and ions? Explain why.

Consider the sodium atom and the sodium ion. (a) Write the chemical symbol of each. (b) Do these particles have the same number of nuclei? (c) Do they have the same number of protons? (d) Could they have different numbers of neutrons? (e) Do they have the same number of electrons?

Define cation, anion, and polyatomic ion.

How many electrons has a titanium atom lost if it has formed the ion \(\mathrm{Ti}^{4+}\) ? What are the total numbers of protons and electrons in a \(\mathrm{Ti}^{4+}\) ion?

If an atom gains an electron to become an ion, what kind of electrical charge does the ion have?

How many electrons has a nitrogen atom gained if it has formed the ion \(\mathrm{N}^{3-}\) ? How many protons and electrons are in an \(\mathrm{N}^{3-}\) ion?

A student wrote the formula for an ionic compound of titanium as \(\mathrm{Ti}_{2} \mathrm{O}_{4}\). What is wrong with this formula? What should the formula be?

What are the formulas (including charges) for (a) cyanide ion, (b) ammonium ion, (c) nitrate ion, (d) sulfite ion, (e) chlorate ion, and (f) sulfate ion?

What are the formulas (including charges) for (a) hypochlorite ion, (b) bisulfate ion, (c) phosphate ion, (d) dihydrogen phosphate ion, (e) permanganate ion, and (f) oxalate ion?

Write the correct formulas for the compounds formed when the following react (a) calcium and chlorine, (b) magnesium and oxygen, (c) aluminum and oxygen, and (d) sodium and sulfur.

Write the unbalanced equations for the following reactions: (a) Iron(III) hydroxide reacts with hydrogen chloride forming water and iron(III) chloride. (b) Silver nitrate is reacted with barium chloride to form silver chloride and barium nitrate.

Write the unbalanced equations for the following reactions: (a) Propane reacts with oxygen to form carbon dioxide and water. (b) Sodium metal is added to water and the products are sodium hydroxide and hydrogen gas.

Which kind of elements normally combine to form molecular compounds?

Without referring to Table 2.6 but using the periodic table, write chemical formulas for the simplest hydrogen compounds of (a) carbon, (b) nitrogen, (c) tellurium, and (d) iodine.

The simplest hydrogen compound of phosphorus is phosphine, a highly flammable and poisonous compound with an odor of decaying fish. What is the formula for phosphine?

Astatine, a member of the halogen family, forms a compound with hydrogen. Predict its chemical formula.

Write the chemical formulas for (a) methane, (b) ethane, (c) propane, and (d) butane. Give one practical use for each of these hydrocarbons.

What are the formulas for (a) methanol and (b) ethanol?

What is the formula for the alkane decane, which has 10 carbon atoms?

Candle wax is a mixture of hydrocarbons, one of which is an alkane with 23 carbon atoms. What is the formula for this hydrocarbon?

The formula for a compound is correctly given as \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\). State two reasons why we expect this to be a molecular compound, rather than an ionic compound.

What is the difference between a binary compound and one that is diatomic? Give examples that illustrate this difference.

Describe (a) the three situations in which Greek prefixes are used and (b) when Roman numerals are used.

The compound \(\mathrm{Cr}\left(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)_{3}\) is used in the tanning of leather. How many atoms of each element are given in this formula?

Asbestos, a known cancer-causing agent, has a typical formula of \(\mathrm{Ca}_{3} \mathrm{Mg}_{5}\left(\mathrm{Si}_{4} \mathrm{O}_{11}\right)_{2}(\mathrm{OH})_{2} .\) How many atoms of each element are given in this formula?

Epsom salts is a hydrate of magnesium sulfate, \(\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O} .\) What is the formula of the substance that remains when Epsom salts is completely dehydrated?

Rochelle salt is the tetrahydrate of \(\mathrm{KNaC}_{4} \mathrm{H}_{4} \mathrm{O}_{6},\) which means there are four molecules of water per \(\mathrm{KNaC}_{4} \mathrm{H}_{4} \mathrm{O}_{6}\) Write the formula for Rochelle salt.

How many atoms of each element are represented in each of the following formulas? For each, name the elements prescnt. (a) \(\mathrm{K}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\) (b) \(\mathrm{H}_{2} \mathrm{SO}_{3}\) (c) \(\mathrm{C}_{12} \mathrm{H}_{26}\) (d) \(\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\), (e) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4}\)

How many atoms of each kind are represented in the following formulas? For each, name the elements present. (a) \(\mathrm{H}_{3} \mathrm{PO}_{4},\) (b) \(\mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2}\), (c) \(\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}\) (d) \(\mathrm{Fe}_{3}\left(\mathrm{AsO}_{4}\right)_{2}\) (e) \(\mathrm{C}_{3} \mathrm{H}_{5}(\mathrm{OH})_{3}\)

How many atoms of each kind are represented in the following formulas? For each, name the elements present. (a) \(\mathrm{Ni}\left(\mathrm{ClO}_{4}\right)_{2},\) (b) \(\mathrm{COCl}_{2}\), (c) \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) (d) \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H},\) (e) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4}\)

How many atoms of each kind are represented in the following formulas? For each, name the elements present. (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CO}_{2} \mathrm{C}_{3} \mathrm{H}_{7}\), (b) \(\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}\) (c) \(\mathrm{KAl}\left(\mathrm{SO}_{4}\right)_{2} \cdot 12 \mathrm{H}_{2} \mathrm{O}\) (d) \(\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}\) (e) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{COH}\)

How many atoms of each element are represented in each of the following expressions? (a) \(7 \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\), (b) \(2\left(\mathrm{NH}_{2}\right)_{2} \mathrm{CO}\) (c) \(5 \mathrm{C}_{3} \mathrm{H}_{5}(\mathrm{OH})_{3}\)

How many atoms of each element are represented in each of the following expressions? (a) \(3 \mathrm{~N}_{2} \mathrm{O},\) (b) \(4\left(\mathrm{CH}_{3}\right)_{2} \mathrm{~S},\) (c) \(2 \mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O}\)

Consider the balanced equation $$ 2 \mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3}+3 \mathrm{Na}_{2} \mathrm{CO}_{3} \longrightarrow \mathrm{Fe}_{2}\left(\mathrm{CO}_{3}\right)_{3}+6 \mathrm{NaNO}_{3} $$ (a) How many atoms of \(\mathrm{Na}\) are on each side of the equation? (b) How many atoms of \(\mathrm{C}\) are on each side of the equation? (c) How many atoms of \(\mathrm{O}\) are on each side of the equation? (d) How many atoms of Fe are on each side of the equation?