Covalent Bonding and Compounds

Question 1

What do covalent substances contain?

Answer 1

Shared pairs of electrons between atoms

Question 2

How do atoms form covalent bonds?

Answer 2

By sharing pairs of electrons with other atoms

Question 3

What does each covalent bond provide to an atom?

Answer 3

One extra shared electron

Question 4

Define covalent bonding

Answer 4

The electrostatic attraction between the negatively charged shared electrons (bonding pair) & the positively charged nuclei of the atoms involved.

Question 5

How many covalent bonds does a hydrogen molecule (H₂) form?

Answer 5

One covalent bond between two hydrogen atoms

Question 6

What type of covalent bond forms between chlorine atoms (Cl₂)?

Answer 6

One covalent bond

Question 7

What type of bond forms in hydrogen chloride (HCl)?

Answer 7

One covalent bond between hydrogen and chlorine

Question 8

How many covalent bonds can nitrogen (N₂) form?

Answer 8

Three covalent bonds (triple bond between two nitrogen atoms)

Question 9

How many covalent bonds are in ammonia (NH₃)?

Answer 9

-Three covalent bonds
-One each with three hydrogen atoms

Question 10

What type of bond is in an oxygen molecule (O₂)?

Answer 10

Double covalent bond between two oxygen atoms

Question 11

How are bonds arranged in a water molecule (H₂O)?

Answer 11

-Oxygen shares one pair of electrons with each hydrogen
-Forms two covalent bonds

Question 12

What bonds are present in carbon dioxide (CO₂)?

Answer 12

Two double covalent bonds between carbon and each oxygen

Question 13

How does methane (CH₄) bond?

Answer 13

-Carbon forms four covalent bonds
-One each with four hydrogen atoms

Question 14

What bonding occurs in ethane (C₂H₆)?

Answer 14

-6 hydrogen atoms each form one bond with a carbon atom
-2 carbon atoms share one covalent bond with each other

Question 15

What bonding is in chloromethane (CH₃Cl)?

Answer 15

-Carbon forms 3 bonds with hydrogen
-1 bond with chlorine

Question 16

What bonding occurs in ethene (C₂H₄)?

Answer 16

-4 hydrogen atoms each bond with carbon
-2 carbon atoms share two covalent bonds (double bond)

Question 17

What holds atoms in a simple molecular substance?

Answer 17

-Strong covalent bonds within molecules
-Weak intermolecular forces between molecules

Question 18

Why do simple molecular substances have low melting/boiling points?

Answer 18

-Weak intermolecular forces
-Molecules are easily separated

Question 19

What happens to melting/boiling points as relative molecular mass increases?

Answer 19

-Intermolecular forces get stronger
-More energy is needed to break them
-Melting/boiling points increase

Question 20

What state are most simple molecular substances at room temperature?

Answer 20

-Gases
-Liquids
-Easily melted solids

Question 21

What are characteristics of giant covalent structures?

Answer 21

-Atoms bonded by strong covalent bonds
-Very high melting and boiling points
-Do not conduct electricity (except graphite)
-Usually insoluble in water

Question 22

What is diamond made of?

Answer 22

A network of carbon atoms

Each carbon forms four covalent bonds

Question 23

Why is diamond hard?

Answer 23

Strong covalent bonds hold atoms in a rigid lattice structure

Question 24

Why does diamond have a high melting point?

Answer 24

Strong covalent bonds take a lot of energy to break

Question 25

Why is diamond hard?

Answer 25

Strong covalent bonds hold atoms in a rigid lattice structure

Question 26

Why doesn’t diamond conduct electricity?

Answer 26

No free electrons or ions

Question 27

How is bonding different in graphite compared to diamond?

Answer 27

Each carbon in graphite forms three covalent bonds Creates layers of carbon atoms

Question 28

Why is graphite soft and slippery?

Answer 28

Layers are held together weakly by intermolecular forces Layers can slide over each other

Question 29

Why does graphite have a high melting point?

Answer 29

Covalent bonds in the layers require a lot of energy to break

Question 30

Why can graphite conduct electricity?

Answer 30

Each carbon has one delocalised electron These electrons are free to move

Question 31

What is the structure of C₆₀ fullerene?

Answer 31

Hollow spheres made of 60 carbon atoms Large covalent molecules, not a giant covalent structure

Question 32

What holds C₆₀ fullerene molecules together and what effect does this have?

Answer 32

Held by intermolecular forces Molecules can slide over each other → material is soft

Question 33

Why is C₆₀ fullerene a solid at room temperature?

Answer 33

Large molecules have relatively strong intermolecular forces

Question 34

Does C₆₀ fullerene conduct electricity? Why or why not?

Answer 34

Has one delocalised electron per carbon Electrons can't move between molecules Therefore, it's a poor conductor of electricity