topic 3 - bonding

Question 1

Explain the formation of ions in ionic compounds from their atoms, in groups 1, 2, 6 and 7

Answer 1

Groups 1+2: lose electrons to form cations
Groups 6+7: gain electrons to form anions

Question 2

When are the endings -ide and -ate used?

Answer 2

-ide: an anion that contains oxygen and at least one other element
-ate: an anion that contains only one element

Question 3

How do you find the formula of an ionic compound by balancing charges?

Answer 3

The charges of ions need to be balanced.
To make a neutral compound one cation needs to combine with an anion - this pairing ensures the compound has an overall neutral charge

Question 4

Explain the structure of an ionic compound

Answer 4

• Lattice structure formed by strong attractions between oppositely charged ions
• Due to the powerful electrostatic forces between the ions, the compound has a HMP/HBP

Question 5

How is a covalent bond formed?

Answer 5

When a pair of electrons is shared between two atoms. This helps them reach a stable state and achieve a strong bond

Question 6

What is the result of covalent bonding?

Answer 6

Molecules are formed, where atoms share electrons to form stable units

Question 7

Recall the typical size (order of magnitude) of atoms and small molecules

Answer 7

Atom: typically about 0.1 to 0.5 nanometres
Small molecules: range from about 0.1 to a few nanometers in size

Question 8

What do dot and cross diagrams represent?

Answer 8

the outer shell electrons of each atom using dots for one element and crosses for another element.

Question 9

Hydrogen (H2) - Dot and cross

Answer 9

• Sharing single electron
• single covalent bond
• diagram displays 2 hydrogen atoms sharing a pair of electrons

Question 10

Hydrochloric acid (HCl) - Dot and cross

Answer 10

• H + Cl share an electron to form a single covalent bond
• hydrogen has 1 electron and chlorine has 7, indicating their sharing to complete their outer shells

Question 11

Water (H2O) - dot and cross

Answer 11

• O2 shares 2 electrons with 2 hydrogen atoms to form 2 covalent bond
• diagram shows O2 sharing 2 pairs of electrons, 1 pair with each hydrogen atom.

Question 12

Methane (CH4) - dot and cross

Answer 12

• Carbon (C) forms 4 covalent bonds, each has 1 H atom by sharing its 4 outer electrons
• diagram shows C sharing 1 electron with each of the 4 H atoms.

Question 13

Oxygen (O2) - dot and cross diagrams

Answer 13

• 2 O2 atoms share 2 pairs of electrons, forming a double covalent bond between them
• diagram displays both oxygen atoms sharing two pairs of electrons.

Question 14

Carbon Dioxide (CO2) - dot and cross

Answer 14

• 1 C atom shares 2 pairs of electrons with 2 O atoms, forming 2 double covalent bonds
• diagram shows C sharing 2 pairs of electrons with each O atom.

Question 15

Why can elements and compounds be classified as ionic?

Answer 15

Result from electron transfer between atoms, forming charged ions that attract each other.

Question 16

Why can elements and compounds be classified as simple molecular (covalent)?

Answer 16

Atoms share electrons, forming weakly bonded molecules with lower melting points and no conductivity.

Question 17

Why can elements and compounds be classified as giant covalent?

Answer 17

Feature strong covalent bonds in extensive networks, resulting in high melting points. Some, like graphite, can conduct electricity.

Question 18

Why can elements and compounds be classified as metallic?

Answer 18

Comprised of metal atoms sharing a “sea” of electrons, leading to good conductivity and other typical metallic properties.

Question 19

Explain how the structure and bonding of substances results in different physical properties

Question 20

Why do ionic compounds have high melting/boiling points?

Answer 20

Due to strong electrostatic forces of attraction between oppositely charged ions, within the lattice structure. A lot of energy is needed to break this attraction.

Question 21

Why do ionic compounds conduct electricity?

Answer 21

When molten and dissolved the ions become free to move and carry the electric charge. (Not in solids as the ions are fixed)

Question 22

Properties of typical covalent, simple molecular substances:

Answer 22

• LMP/LBP
• Don’t conduct electricity
• Some are soluble in water, some aren’t

Question 23

Why do typical covalent, simple molecular compounds have low melting/ boiling points?

Answer 23

Mostly gases or liquids at room temp, as the molecules get smaller, less energy is needed to break the weaker forces between them

Question 24

Why do typical covalent, simple molecular compounds not conduct electricity?

Answer 24

There are no charged particles to carry charge

Question 25

What are giant covalent structures?

Answer 25

Solids containing atoms which are all bonded to each other by strong covalent bonds

Question 26

3 properties of giant covalent structures:

Answer 26

1. HMP/HBP - Lots of energy needed to overcome strong covalent bonds
2. Don’t conduct electricity (except for a couple exceptions) - no charged particles to carry charge
3. Not soluble in water

Question 27

What are graphite and diamond?

Answer 27

• examples of giant covalent substances
• both carbon allotropes (different forms of carbon)

Question 28

Diamond (bonding, properties, conductivity, uses)

Answer 28

Bonding: C atoms form 4 covalent bonds
Properties: Very hard
Conductivity: doesn’t conduct electricity
Uses: cutting tools (because of hardness)

Question 29

Graphite (bonding, properties, conductivity, uses)

Answer 29

Bonding: C atoms form 3 covalent bonds. No covalent bonds between layers
Properties: soft, slippery
Conductivity: conducts electricity and heat
Uses: electrodes (conductor), lubricant (lubricating)

Question 30

Describe structure of diamond:

Answer 30

C atoms form a rigid 3D lattice, each C atom bonds to 4 others in a 3D lattice, creating extreme hardness.

Question 31

Describe structure of graphite:

Answer 31

C atoms form layers with strong bonds within each layer but weak forces between them, allowing for lubrication and conductivity along the layers.

Question 32

What is a fullerene?

Answer 32

Have hollow shapes, giving them large surface areas

Question 33

Properties of C60 (structure and bonding)

Answer 33

Structure: spherical C molecules with rings of 6 C atoms (sometimes 5 or 7), in hexagons
Bonding: strong covalent bond between C atoms creating a closed cage structure

Question 34

Properties of graphene (structure and bonding)

Answer 34

Structure: Single layer of carbon atoms arranged in a 2D hexagonal lattice.
Bonding: C atoms form 3 strong covalent bonds between C atoms