Chapter 3

If one considers just the representative elements, how many groups would the periodic table have?

Give the names associated with groups IA (1), IIA (2), VIA (16), VIIA (17), and VIIIA (18).

What element seems poorly placed in group IA (1), the alkali metals? Why?

How does a group differ from a period in the periodic table?

Suppose you added one electron and one proton to an atom somewhere in the middle of a period. Which way would this move you on the periodic table and by how many places?

Magnesium (Mg) reacts with chlorine \(\left(\mathrm{Cl}_{2}\right)\) to form the compound \(\mathrm{MgCl}_{2}\). (a) Predict the formulas for the compounds formed when all the other alkaline earth metals react with chlorine. (b) Predict the formulas for the compounds formed when all the alkaline earth metals react with bromine. (c) Explain what principle you used to make your predictions.

State two things that are unique about the noble gases.

Name and give symbols for five of the transition metals.

How many elements are in each transition metal period of the periodic table? How many are in each lanthanide (rare earth)/actinide period?

Metals are excellent conductors of electricity. Nonmetals are poor conductors of electricity and are called insulators. Some elements have the ability to conduct electricity roughly between that of metals and nonmetals. Give some examples of these elements, and name the class they belong to.

It always takes energy to remove an electron from a neutral atom. Explain why, and name the minimum amount of energy it takes to do this.

A student claims that the way to convert a neutral atom of \(\mathrm{Cl}\) into a \(\mathrm{Cl}^{-}\) anion is to decrease its atomic number by one while leaving the number of electrons unchanged. (a) Will this give the atom a \(-1\) charge and convert it into an anion? Explain. (b) Will the atom still be an atom of the element chlorine? Explain. (c) What should the student have done?

What would the charge on a ion be if, starting from the neutral atom: (a) You add three electrons. (b) You remove four electrons. (c) You add two neutrons to the nucleus.

Two students are studying using a plastic model of the atom to which they can easily add or remove electrons, protons, and neutrons. They build a model for the neutral \({ }_{6}^{14} \mathrm{C}\) atom. Their next job is to make the \(+2\) ion of this carbon isotope. Student \(\mathrm{X}\) removes two electrons from the atom. Student \(\mathrm{Y}\) adds two protons to the atom's nucleus. Did both students successfully construct a \(+2\) carbon-14 cation? Explain.

Fill in the following table: $$ \begin{array}{lcccc} & { }_{8}^{15} \mathrm{O}^{+} & ? & ? & ? \\ \hline \text { Mass number } & ? & 27 & ? & 58 \\ \text { Atomic number } & ? & ? & 15 & ? \\ \text { Number of protons } & ? & 13 & ? & ? \\ \text { Number of neutrons } & ? & ? & 16 & 30 \\ \text { Number of electrons } & ? & ? & ? & 27 \\ \text { Charge on ion } & ? & +3 & -3 & +1 \\ \hline \end{array} $$

A student says that it is possible for an atom's second ionization energy to be zero because all the work was done creating a cation with the first jonization energy. Is this student right or wrong? Explain.

What is the trend in first ionization energy as you go down a given group in the periodic table? As you go across a period from left to right?

Give the full symbol for the \(+2\) alkaline earth cation that is in the fourth period and has a mass number 21 greater than its atomic number. Explain.

Of the atoms \(\mathrm{Na}, \mathrm{Mg}\), and \(\mathrm{Al}\), which should be the most difficult to ionize? Which has the smallest first ionization energy?

Of the atoms \(\mathrm{Na}, \mathrm{Mg}\), and \(\mathrm{K}\), which should be the most difficult to ionize? Which has the smallest first ionization energy?

In the reaction of lithium, \(\mathrm{Li}\), with nitrogen, \(\mathrm{N}_{2}\) three lithium atoms react with one nitrogen atom to give the compound \(\mathrm{Li}_{3} \mathrm{~N}\). Atoms of one of these elements lose one electron; atoms of the other element gain three electrons. (a) Which element gains the three electrons? Explain your choice. (b) Does the element that gained three electrons become a cation or an anion? (c) Give the full atomic symbol for the ion of part (b), assuming it has seven neutrons in its nucleus.

White light from an incandescent light bulb gives a continuous visible spectrum when the light is passed through a prism. What is meant by the word continuous in this context?

A heated gas made up of individual atoms gives off a line spectrum when the emitted light is passed through a prism. How does a line spectrum differ from a continuous spectrum?

A \(34.01-g\) sample of pure hydrogen peroxide produced at a chemical company contains \(32.00 \mathrm{~g}\) of oxygen. The rest of the mass is due to hydrogen. (a) What is the percent by mass of oxygen and hydrogen in this sample? (b) Another company also produces pure hydrogen peroxide. What is the percent by mass hydrogen and oxygen in its hydrogen peroxide? What chemical law allowed you to answer this question? (c) A \(91.83-\mathrm{g}\) sample of pure hydrogen peroxide is obtained. How many grams of it are oxygen?

Tin, Sn, and oxygen can combine to form two different compounds called oxides. Oxide A contains \(78.77 \%\) by mass tin. Oxide B contains \(88.12 \%\) by mass tin. What is the percent by mass of oxygen in each oxide?

When wood burns, it combines with oxygen from the atmosphere to produce carbon dioxide, water vapor, and ash. What would you have to do to prove that the law of conservation of matter is not disobeyed when wood burns?

What evidence exists to support the theory that an atom contains a massive nucleus that is very small relative to the size of the whole atom?

When \(5 \mathrm{~g}\) of compound \(\mathrm{A}\) reacts with an unlimited amount of compound \(\mathrm{B}, 7 \mathrm{~g}\) of compound \(\mathrm{C}\) is formed. How many grams of compound B must have reacted, and what law allows you to answer the question?

A student claims that isotopes of the same element have the same number of electrons and protons. Is she correct? Justify your answer.

A student claims that isotopes of the same element have the same number of neutrons but different numbers of protons. Is he correct? Justify your answer.

How do you convert a neutral sulfur atom to an anion carrying a charge of \(2-?\)

A student says that the easiest way to convert a neutral sodium atom to a \(\mathrm{Na}^{+}\) cation is to add a proton to its nucleus. She reasons that this is \(\mathrm{so}\) because protons have a \(1+\) charge. What is wrong with her argument? What does a neutral Na atom become when a proton is added to its nucleus?

The mass number of a neutral atom is 19 , and its atomic number is 9 . The atom contains how many protons, electrons, and neutrons?

The mass number of a \(2+\) cation is 56 , and its atomic number is 26 . The ion contains how many protons, electrons, and neutrons?

How many protons, electrons, and neutrons are there in: (a) \(^{79} \underline{\mathrm{Br}}\) (b) \(^{81} \mathrm{Br}^{-}\) (c) \({ }^{23} \mathrm{Na}^{+}\) (d) \({ }^{3} \mathrm{H}^{+}\)

The element nitrogen has only two naturally occurring isotopes: \({ }^{14} \mathrm{~N}\) with a mass of \(14.00308\) amu and an abundance of \(99.635 \%\) and \({ }^{15} \mathrm{~N}\) with a mass of \(15.00011\) amu and an abundance of \(0.3650 \%\). Calculate the atomic mass of nitrogen.

Silver has only two naturally occurring isotopes: \({ }^{107} \mathrm{Ag}\) with a mass of \(106.90509 \mathrm{amu}\) and an abundance of \(51.84 \%\) and \({ }^{109} \mathrm{Ag}\) with a mass of \(108.9047\) amu. Calculate the atomic mass of silver.

Mendeleev arranged the elements by atomic mass and then separated them into various groups. What was his criterion for which elements were grouped together?

Arrange \(\mathrm{Na}, \mathrm{Cs}, \mathrm{S}, \mathrm{Cl}\) in order of increasing first ionization energy.

Scandium (Sc) is a metal that tends to lose three electrons. Copper (Cu) and zinc \((Z n)\) are also metals that tend to lose one and two electrons, respectively. Knowing this, explain why the first group in the transition metals is numbered IIIB, whereas the last two groups in the transition series are numbered IB and IIB, respectively.

How many electrons are there in \(\mathrm{Zr}^{4+}\) ? What \(2+\) cation has the same number of electrons as \(\mathrm{Zr}^{4+} ?\)

How many electrons are there in Br'? What \(1+\) cation has the same number of electrons as Br"?

What is the identity of element \(X\) if its \(2+\) cation contains ten electrons?

Magnesium has a higher first ionization energy than sodium, consistent with the periodic trend for first ionization energies. Postulate a reason why Mg has the higher first ionization energy.

A \(110.99-g\) sample of a compound containing only calcium and chlorine is found to contain \(40.98 \mathrm{~g}\) of calcium. (a) How many grams of chlorine are in the compound? (b) What is the percent by mass of calcium in the compound? (c) What is the percent by mass of chlorine in the compound?

Explain the major difference between Thomson's model of the atom and Rutherford's model. Draw a picture of each model.

Examine the periodic table that lists the first ionization energies of the elements, and state the trend for first ionization energies when you go down any group.

How does the arrangement of elements in the modern periodic table differ from that of Mendeleev's periodic table?

Write the elemental symbols for nitrogen, silicon, phosphorus, potassium, and gold.

List three properties of metals and two properties of nonmetals. Describe the behavior of metalloids relative to the behaviors of metals and nonmetals.