Chapter 4

 

Modified True/False

Indicate whether the sentence or statement is true or false.  If false, change the identified word or phrase to make the sentence or statement true.

 

____          1.   Carbon dioxide is present at a higher concentration in air that is exhaled than in air that is inhaled.

 

____          2.   The most abundant element in the universe is oxygen.

 

____          3.   The elements in column 18 of the periodic table are chemically inactive.

 

____          4.   A typical potassium ion has a positive charge because it has lost an electron.

 

____          5.   The formula for methane, CH₄, indicates that each methane molecule contains one carbon atom and four hydrogen atoms.

 

Multiple Choice

Identify the letter of the choice that best completes the statement or answers the question.

 

____          6.   The properties of a compound are _____ the properties of the elements that form it.

a.	similar to	c.	identical to
b.	different from	d.	derived from

 

 

____          7.   A colorless, odorless gas combines with a magnetic, metallic element. What can you predict about the product?

a.	It will also be magnetic.
b.	A gas and a solid produce a liquid.
c.	The compound will be shiny and odorless.
d.	It is impossible to predict its specific properties.

 

 

____          8.   Noble gases _____.

a.	form no compounds
b.	form compounds easily
c.	form no compounds that occur naturally in the environment
d.	do not obey the octet rule

 

 

____          9.   Think of the terms octet, octopus, and octagon. Infer the meaning of the prefix oct-.

a.	shape	c.	stable
b.	eight	d.	multi-

 

 

____          10.  Oppositely charged ions attract each other, forming a(n) _____ bond.

a.	covalent	c.	ionic
b.	crystal	d.	molecular

 

 

____          11.  The strong crystal structure of an ionic compound is one reason ionic compounds have _____ melting points.

a.	high	c.	moderate
b.	low	d.	variable

 

 

____          12.  The formula for iron(III) oxide, Fe₂Cl₃, shows that one unit of the compound contains _____ iron atoms.

a.	2	c.	5
b.	3	d.	6

 

 

____          13.  Lithium has much less attraction for any valence electrons than does fluorine. Atoms of these two elements would form _____ bonds.

a.	covalent	c.	crystal
b.	ionic	d.	molecular

 

 

____          14.  Two atoms of bromine react with each other to form a(n) _____ bond.

a.	covalent	c.	crystal
b.	ionic	d.	molecular

 

 

____          15.  Electron sharing produces _____.

a.	crystals	c.	molecules
b.	ions	d.	liquids

 

 

____          16.  Nitrogen atoms each have five valence electrons. How many pairs of electrons must be shared in a molecule of N₂?

a.	1	c.	4
b.	3	d.	6

 

 

____          17.  Noble gases are sometimes used to protect valuable documents because they are _____.

a.	molecular	c.	unreactive
b.	totally inert	d.	unstable

 

 

____          18.  When reacting with an atom of fluorine, an atom of lithium will lose an electron and become a lithium _____.

a.	compound	c.	ion
b.	crystal	d.	molecule

 

 

____          19.  When an atom loses an electron, it becomes a _____ ion.

a.	negative	c.	neutral
b.	positive	d.	polyatomic

 

 

____          20.  A regular, repeating arrangement of atoms, ions, or molecules is _____.

a.	amorphous	c.	a compound
b.	a crystal	d.	impossible to break down

 

 

Completion

Complete each sentence or statement.

 

                  21.  A(n) _______________ is an atom or group of atoms that carries an electric charge because it has gained or lost electrons.

 

                  22.  A(n) _______________ is a substance that conducts an electric current when dissolved in water or when melted.

 

                  23.  The bond formed when one atom transfers one or more electrons to a second atom is called a(n) _______________.

 

                  24.  A(n) _______________ shows in a shorthand way the numbers and kinds of elements present in a compound.

 

                  25.  According to the principle called the _______________, an atom is stable when it has eight electrons in its outer energy level.

 

Problem

 

Look at each of the electron dot structures shown below. In each case, decide: how many valence electrons are present; whether or not the particle is reactive; and if it is reactive, what it could do to become part of a stable compound and what kind of bond it would form in the process.

 

                  26.  Rb·

 

                  27.  ..

:Ne:

 ··

 

                  28.    .. 

[:Br:]^-

  ··

 

Listed below are some imaginary data for a series of compounds. Based on what you have learned, predict whether each compound is probably ionic (I) or covalent (C). If the information given might apply to either kind of compound, put a question mark (?).

 

                  29.  Is a white solid at -100ºC.

 

                  30.  Is a hard, rough crystal.