AnswersNC-Physical Science Fall 1st 9 WeeksCovalent Bonds

Covalent Bonds — Unit test Answers

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How many atoms of each element are in the chemical formula Ca(OH)2?

A
1 calcium, 1 oxygen, and 1 hydrogen
B
1 calcium, 2 oxygen, and 2 hydrogen
C
2 calcium, 1 oxygen, and 2 hydrogen
D
2 calcium, 2 oxygen, and 2 hydrogen
2
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Which refers to the type of chemical bond that involves the transfer of electrons between atoms?

A
metallic
B
polar covalent
C
ionic
D
covalent
3

There are several different models that represent compounds. One type of model is shown.

Question illustration
A
a structural formula
B
a chemical formula
C
a space-filling model
D
a ball-and-stick model
4

Which is most likely a covalent compound?

A
LiF
B
MgS
C
NH3
D
CaCl2
5

What best explains whether bromine (Br) or neon (Ne) is more likely to form a covalent bond?

Question illustration
A
Bromine forms covalent bonds because it has seven valence electrons, but neon has eight valence electrons and already fulfills the octet rule.
B
Bromine forms covalent bonds because it has many electron shells, but neon has only two electron shells and is tightly bound to its electrons.
C
Neon forms covalent bonds because it can share its valence electrons, but bromine has seven valence electrons and can gain only one more electron.
D
Neon forms covalent bonds because it has only two electron shells, but bromine has many electron shells and will lose electrons in order to fulfill the octet rule.
6

Sal drew the electron dot diagram of an aluminum atom as shown.

Question illustration
A
He should add five more dots so that the atom obeys the octet rule.
B
He should add ten more dots so that all thirteen electrons are shown.
C
He should add a single dot below the symbol.
D
He should add one dot below and one dot to the left of the symbol.
7

The table describes the properties of four compounds.Which compounds are most likely ionic?

Question illustration
A
compounds A and B
B
compounds B and C
C
compounds C and D
D
compounds D and A
8

Which is a characteristic of all ions?

A
They are metals.
B
They have a charge.
C
They are made of two or more types of atoms.
D
They form chemical bonds through electron sharing.
9

Shameeka is studying for an exam. She took the notes below about calcium and chlorine, which are known to form ionic bonds.Calcium, which is a metal, donates 2 electrons to chlorine.The individual calcium atoms become ions with a negative 2 charge. The bond between calcium and chlorine makes the atoms stable. Calcium and chlorine attract each other. Which best describes Shameeka’s error?

A
Calcium is a metal, so it donates protons, not electrons.
B
The individual calcium atom has a positive, not negative, 2 charge.
C
The bond formed makes the atoms unstable, not stable.
D
Calcium and chlorine repel, not attract, each other.
10

"Na2SO3” represents sodium sulfite.What does the 4 mean in the formula 4Na2SO3?

A
There are four atoms of sodium.
B
There are four atoms of sodium sulfite.
C
There are four formula units of sodium sulfite.
D
There are four elements in sodium sulfite.
11

What does the octet rule state that explains why atoms bond?

A
An atom bonds to have eight valence electrons to become stable.
B
An atom bonds to lose eight valence electrons to become stable.
C
An atom bonds to have eight valence electrons to become unstable.
D
An atom bonds to lose eight valence electrons to become unstable.
12

Which ionic compound is used as a building material?

A
salt
B
limestone
C
magnesium oxide
D
iron oxide
13

An atom of lithium (Li) forms an ionic bond with an atom of chlorine (Cl) to form lithium chloride. How are the valence electrons of these atoms rearranged to form this bond?

A
A few valence electrons are shared between the atoms.
B
Many valence electrons are shared between the atoms.
C
Electrons are transferred from the chlorine atom to the lithium atom.
D
Electrons are transferred from the lithium atom to the chlorine atom.
14

Calcium carbonate (CaCO3) is a white solid with no odor. When CaCO3 is heated, the resulting substances are calcium oxide (CaO) and carbon dioxide (CO2). CaO is a white to gray solid with no odor, and CO2 is a gas with no odor and color.Which statement describes CaCO3?

A
It is a diatomic molecule that can’t be broken down by physical means.
B
It is a diatomic molecule that can’t be broken down by chemical means.
C
It is a compound that can be broken down by physical means.
D
It is a compound that can be broken down by chemical means.
15

To what extent do covalent compounds conduct electricity?

A
always
B
usually
C
rarely
D
never
16

Which describes the substances that form covalent bonds?

A
a metal and a metalloid
B
a metal and a nonmetal
C
two nonmetals
D
two metals
17

How many dots belong in the electron dot diagram of a boron (B) atom?

A
three
B
five
C
eight
D
thirteen
18

Chalk is an ionic compound. Which is a property of all ionic compounds that makes chalk particularly useful for writing on a chalkboard?

A
a high melting point
B
hardness and brittleness
C
inability to dissolve in water
D
a multicolored appearance
19

There are several ways to model a compound. One type of model is shown.

Question illustration
A
CHO
B
C4H11O2
C
C6H12O2
D
C6H9O
20

What is formed when polyatomic ions bond with other ions?

A
ionic compounds
B
neutral compounds
C
ionic elements
D
neutral elements

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