Chemical Bonding Multiple Choice with answer key

You may use a periodic table and a calculator to do this test. 

 

Multiple-choice section

Please write the letter of the most correct answer in the space next to the problem for each of the following ten problems:

1)         How many valence electrons does gallium have?

            a)         1                                             c)         5

            b)        3                                             d)        13

2)         How many electrons does phosphorus have to gain in order to achieve a noble-gas electron configuration?

            a)         2                                             c)         5

            b)        3                                             d)        4

3)         How many valence electrons are transferred from the nitrogen atom to each potassium in the formation of the compound potassium nitride?

            a)         0                                             c)         3

            b)        1                                             d)        5

4)         Which of the following takes place in an ionic bond?

            a)         Two atoms share two electrons

            b)        Two atoms share electrons such that both follow the octet rule.

            c)         Like-charged ions attract

            d)        Oppositely-charged ions attract

5)         What is the net charge of the ionic compound calcium fluoride?

            a)         -2                                            c)         +2

            b)        0                                             d)        -1

6)         Ionic compounds are normally found in what state at room temperature?

            a)         solid                                       c)         gas

            b)        liquid                                      d)        none of these

7)         The melting temperature of potassium chloride is relatively…

            a)         low                                         c)         KCl does not melt

            b)        high                                        d)        about room temperature

8)         What does the term “coordination number” refer to?

            a)         The number of oppositely charged ions surrounding a particular ion

            b)        The number of atoms in a unit cell

            c)         The number of valence electrons in an atom

            d)        The number of times a compound forms covalent bonds

9)         What characteristic of metals makes them good electrical conductors?

            a)         Mobile valence electrons

            b)        Mobile protons

            c)         Their crystal structures rearrange easily

            d)        Mobile cations

10)       How many electrons are shared between two atoms in a double covalent bond?

            a)         8                                             c)         4

            b)        6                                             d)        2

11)       How many unshared pairs of electrons are there in hydrogen iodide?

            a)         1                                             c)         3

            b)        6                                             d)        none of these

12)       Which of the following elements occurs naturally as a diatomic molecule with three covalent bonds?

            a)         oxygen                                               c)         fluorine

            b)        hydrogen                                d)        nitrogen

13)       When one atom contributes both bonding electrons in a single covalent bond, the bond is called a(n)…

               a)      ionic covalent bond

            b)        polar covalent bond

            c)         one-sided covalent bond

            d)        coordinate covalent bond

14)       Which of the following pairs of elements can be joined by a covalent bond?

            a)         Li and Br                                c)         Mg and C

            b)        N and C                                               d)      He and O

15)       In which of the following compounds/ions is there an exception to the octet rule?

            a)         SF₆                                         c)         MgO

            b)        PH₃                                         d)        BH₄⁺¹

 

Answer Key:

1)         b – Valence electrons are the number of s- and p-electrons since the last noble gas.  The d-electrons don’t count.

2)         b – It has five valence electrons, and wants eight like argon.

3)         a – Electrons are transferred from K to N, not the other way around.

4)         d

5)         b – Ionic compounds have no overall charge, because the cations and anions cancel each other out.

6)         a – Ionic compounds generally have high melting and boiling points because the positive and negative charges are tightly bound to one another.

7)         b – See explanation above

8)         a

9)         a – If this doesn’t make sense, study the “electron sea theory” of metallic bonding.

10)       c – Because each bond contains two electrons, a double bond will contain 4 electrons.

11)       c – All three unshared electron pairs are on the iodine atom.

12)       d – The others are all naturally diatomic, but only N₂ has triple bonds.

13)       d

14)       b – The differences in electronegativity between the other elements are too large for covalent bonding to occur.

15)       a – Sulfur has six electron pairs around it.