Covalent bonding (Chapter 8)

Question 1

What is covalent bond?

Answer 1

In a covalent bond, a pair of electrons is shared between two atoms.

Question 2

What is covalent bond held by?

Answer 2

It is held by strong electrostatic attraction between the nuclei of the atom and the shared pair of electrons.

Question 3

What is diatomic atoms?

Answer 3

Diatomic molecules contain 2 atoms.

Question 4

What do we call atoms which have same number of electrons in their outer shells as a noble gas atom?

Answer 4

Isoelectronic of the noble gas atom.

Question 5

What happen when atom can form more bonds?

Answer 5

The more bonds atom can form, the more energy is release and the more stable the system becomes.

Question 6

The lower the energy molecule has, —— it become.

Answer 6

The more stable

Question 7

Why molecules with more bonds are more stable?

Answer 7

When more bonds form, more energy is released making the result substance to have lower energy, making it more stable.

Question 8

Pair of electrons in the outer shell of the central atom _____ each other.

Answer 8

repel

Question 9

What is double and triple covalent bond?

Answer 9

Double covalent bond - molecules that have 2 shared pairs of electrons between atoms
Triple covalent bond - molecules that have 3 share pairs of electrons between atoms

Question 10

What is intermolecular force?

Answer 10

Force of attraction between same molecules which hold them together.

Question 11

Which is weaker, intermolecular force between molecules or covalent bonds?

Answer 11

Intermolecular force between molecule.

Question 12

What is simple molecular structure?

Answer 12

Substance that consists of molecules with intermolecular force of attraction between them.

Question 13

Which states does substances with simple molecular structure tend to stay?

Answer 13

Gas or liquid

Question 14

Why substances with simple molecular structure have low melting and boiling point?

Answer 14

Because not much energy is required to break the weak intermolecular force of attraction between molecules.

Question 15

The relative molecular increase, their melting point and boiling point —–.

Answer 15

Increase

Question 16

The more relative molecular, the —– the intermolecular attraction between molecules.

Answer 16

stronger

Question 17

What are physical properties of covalent compounds?

Answer 17

• They don’t conduct electricity
• They tend to be insoluble in water
• They are often soluble in covalent compounds

Question 18

Why covalent molecules do not conduct electricity?

Answer 18

Because the molecules don’t have any overall electrical charge and all electrons are held tightly in the atoms or in covalent bonds.

Question 19

Why diamond has high melting and boiling point?

Answer 19

Because of the very strong carbon-carbon covalent bonds, which extend throughout the whole crystal in three dimensions.

Question 20

Why does diamond not have no intermolecular force?

Answer 20

Because it has giant structure, so, it has no molecules.

Question 21

Which state does substances with giant covalent structure tend to stay?

Answer 21

Solid

Question 22

What are some examples of giant covalent structures?

Answer 22

Diamond, graphite, silicon dioxide

Question 23

Does diamond conduct electricity?

Answer 23

No, because all the electrons in the outer shells of carbon atoms are tightly held in covalent bonds between the atoms.

Question 24

Diamond can conduct heat very well.

Answer 24

True

Question 25

What kind of structure does graphite have?

Answer 25

Giant structure composed in layers

Question 26

Where are graphite used?

Answer 26

In pencils

Question 27

Graphite has _____ melting and boiling point.

Answer 27

High

Question 28

Why does graphite conduct electricity?

Answer 28

Because each carbon atoms forms three covalent bonds sharing three electrons and the remaining fourth one is free to move around throughout the whole layer.

Question 29

What are delocalized electrons?

Answer 29

The electrons that are free to move throughout the layers.

Question 30

What are the allotropes of carbon?

Answer 30

Diamond, graphite and fullerene

Question 31

What are allotropes?

Answer 31

Allotropes are different forms of the same element.

Question 32

What are properties of fullerene?

Answer 32

• It has lower melting and boiling point than diamond and graphite
• It is not as hard as diamond
• It doesn’t conduct electricity
• It can dissolve in some solvent

Question 33

Why fullerene does not conduct electricity?

Answer 33

Although all carbon atoms of fullerene forms three bonds, the fourth electron on each atom can only move around within each fullerene molecule.

Question 34

What are properties of graphite?

Answer 34

• It has high melting point and boiling point
• It conducts electricity
• It is insoluble in all solvents
• It is less dense than diamonds

Question 35

Which kind of structure does fullerene have?

Answer 35

Simple molecular structure