COVALENT BONDING [dchemlc]

which of the following statements is incorrect about diamond?

• Diamond has a low melting and boiling point.

• carbon atoms in diamond are arranged in a tetrahedral arrangement

• Diamond is very hard

• Diamond doesn't conduct electricity

Answer explanation

Diamond has a very high melting and boiling point.

This is because of the very strong carbon-carbon covalent bonds, which extend throughout the whole crystal in three dimensions. A lot of energy has to be supplied to break these strong covalent bonds, therefore diamond has very high melting and boiling points.

which of the following is not an allotrope of carbon?

• methane

• diamond

• graphite

• fullerene

Answer explanation

Methane has the formula CH_4.

Therefore, it cannot be an allotrope of carbon.

which of the following statements is incorrect about graphite?

• Graphite has a simple molecular structure.

• Graphite conducts electricity

• Graphite has high melting and boiling points.

• Graphite is a soft material.

Answer explanation

graphite is a giant covalent structure.

which of the following is not true about covalent compounds?

• covalent compounds conduct electricity

• covalent bond is formed between atoms by the sharing of a pair of electrons

• Covalent substances are often soluble in organic solvents.

• Covalent substances tend to be insoluble in water.

Answer explanation

Covalent molecular compounds do not conduct electricity.

which of the following molecules are diatomic with a triple bond between the two atoms?

• N2

• H2

• O2

• HCl

Answer explanation

Did you realize that HCl is not even a diatomic molecule?

WOWW!!

YOU'RE SMARTER THAN YOU THINKK.

KEEP IT UP!!!

Substances with simple molecular structures tend to be gases or liquids or solids with low melting points and boiling points. What is the reason for this?

• they have weak intermolecular forces of attractions

• they have weak covalent bonds

• they have weak ionic bonds

• they have weak electrostatic forces of attraction between atoms

Answer explanation

The reason for this is that not much energy is required to break the weak intermolecular forces of attractions between molecules. Remember, no covalent bonds are broken, covalent bonds are strong.

what holds the atoms together in a covalent bond?

• the strong electrostatic attraction between the nuclei of the atoms that make up the bond, and the shared pair of electrons

• the strong electrostatic attraction between cations and anions

• the strong electrostatic attraction between electrons of one atom with the electrons of the adjacent atom

• the strong electrostatic forces of attraction between each positive ion and the delocalised electrons.

Answer explanation

What holds the atoms together is the strong electrostatic attraction between the nuclei (positively charged) of the atoms that make up the bond, and the shared pair of electrons (negatively charged).

which of the following covalent compounds do not have 8 electrons in the central atom?

• SO₂

• CH₄

• C₂H₄

• CO₂

Answer explanation

Although the outer atoms in a molecule will always have 8 (or 2 in the case of hydrogen) electrons in their outer shell, there are a few examples you may encounter where the central atom has more or fewer than 8 electrons in the outer shell.

e.g. BF₃

SO₂

which of the following statements is not true about C₆₀ fullerene?

• C₆₀ fullerene has a giant covalent structure

• C₆₀ fullerene does not conduct electricity

• C₆₀ fullerene is not as hard as diamond

• C₆₀ fullerene has lower melting and boiling points than diamond and graphite

Answer explanation

Diamond and graphite both have giant structures but C₆₀ fullerene has a simple molecular structure.

which of the following is not a covalent compound?

• 
• 
• 
• 

Answer explanation

were you able to figure out which of these diagrams was not a dot and cross diagram?

WELL DONE!!!!