3.1.3 - Bonding

Question 1

Define ‘ionic bonding’

Answer 1

Ionic bonding: electrostatic attraction between oppositely charged ions in a lattice.

Question 2

Describe the physical features of ionic substances x3

Answer 2

Ionic substances are always solid at room temperature, brittle and shatter easily.

Question 3

How do you strengthen ionic bonding?

Answer 3

• Greater charge on the ions.
• Smaller ions.
• > Higher charge density
• > Stronger ionic bonding

Question 4

Ionic compounds involve a metal and metal. True/false?

Answer 4

False: Ionic compounds involve a metal and non-metal.

Question 5

When can ionic compounds conduct electricity and why?

Answer 5

Ionic compounds cannot conduct electricity when solid, but can when molten/dissolved in water, as ions can move to carry a charge.

Question 6

Do ionic substances have low or high mpts/bpts? Why?

Answer 6

Because ionic compounds are in a giant ionic lattice, there are strong electrostatic forces of attraction between oppositely charged ions acting in all directions, thus they have high mpts/bpts.

Question 7

When is an ionic subtance purely ionic in bonding?

Answer 7

With the Pauling’s Scale, a difference of 1.7 or over between the elements means that the bond is purely ionic.

Question 8

Define ‘covalent bond’

Answer 8

A chemical bond formed by the sharing of pairs of electrons between atoms.

Question 9

‘A single covalent bond contains a ______ ______ of electrons. Multiple bonds contain ________ pairs of electrons.’


Answer 9

‘A single covalent bond contains a shared pair of electrons. Multiple bonds contain multiple pairs of electrons.’


Question 10

What is it called when one atom donates both electrons in the shared electron pair of a covalent bond? Example?

Answer 10

‘A co-ordinate (dative covalent) bond contains a shared pair of electrons with both electrons supplied by one atom.’ E.g. NH4+

Question 11

Covalent bonding occurs…?

Answer 11

Between non-metals.

Question 12

Simple molecular substances have a ______ structure

Answer 12

Molecular (non-lattice) structure.

Question 13

Do simple molecular substances have low or high mpts/bpts? Why?

Answer 13

Low, because only weak IMFs exist between molecules, which require little energy to overcome and break.

Question 14

Can simple molecular substances conduct electricity and why?

Answer 14

No - no delocalised electrons or ions to move and carry the charge.

Question 15

What is a dimer? Example?

Answer 15

A ‘dimer’ is 2 of the same molecule bonded together in order to satisfy the electron arrangements of each atom, e.g. AlCl3

Question 16

How are atoms in a simple molecular substance held together?

Answer 16

Covalent bonds: atoms are held together by each nucleus pulling on the electrons.

Question 17

Which are stronger, covalent bonds or dative covalent/coordinate bonds?

Answer 17

In dative covalent bonds, the 2 electrons still come under equal influence of the forces of attraction to the nuclei, thus dative covalent bonds are of the same strength as covalent bonds.

Question 18

Define ‘metallic bonding’.

Answer 18

‘Metallic bonding involves attraction between delocalised electrons and positive ions arranged in a lattice.’

Question 19

Do metals have high/low bpt/mpts and why?

Answer 19

HIGH - Metallic bonds are strong and a lot of energy is needed to break them. This is why metals have high melting points and boiling points. The bonds are strong attraction between closely packed positive metal ions and a ‘sea’ of delocalised electrons.

Question 20

When do metals conduct electricity and why?

Answer 20

Both when solid and dissolved/molten, as delocalised electrons can move through the structure and carry a charge.’When a potential difference is applied, they will move together, allowing an electric current to flow through the metal.’

Question 21

How do we get stronger metallic bonding and why?

Answer 21

• Smaller the metal ions
• Greater the charge on the ions (more delocalised outer shell electrons)
• > Stronger attraction between the ions and electrons (usually). = This is due to a greater charge density within the structure.

Question 22

Solubility of metals in water?

Answer 22

Insoluble.

Question 23

Solubility of macromolecules in water?

Answer 23

Insoluble.

Question 24

Mpts/bpts of macromolecules and why?

Answer 24

High - strong covalent bonds in a giant structure.

Question 25

Conductivity of electricity in macromolecules when solid?

Answer 25

Diamond - X
Graphite - YES, due to one delocalised electron per carbon that can move along the planes of carbon atoms, between the layers.

Question 26

Conductivity of electricity in macromolecules when molten?

Answer 26

Poor.

Question 27

What physical state do most simple molecular substances take at room temp?

Answer 27

Liquid/gas.

Question 28

Physical properties of metals? x3

Answer 28

• Shiny.
• Crystalline solids (at room temp).
• Malleable (as the positive ions in the lattice are all identical, so the planes of ions can easily slide over one another).

Question 29

A change of state directly from solid to gas is called…?

Answer 29

A change of state directly from solid to gas is called ‘sublimation’.

Question 30

Define ‘enthalpy’.

Answer 30

Enthalpy is the amount of heat content used or released in a system at constant pressure.

Question 31

Solid -> liquid: latent heat of ________

Answer 31

Latent heat of fusion

Question 32

Liquid -> gas: latent heat of ________

Answer 32

Latent heat of vaporisation

Question 33

Lone pair–lone pair repulsion is ________ than lone pair–bond pair repulsion, which is ________ than bond pair–bond pair repulsion:
lp-lp __ lp-bp __ bp-bp.

Answer 33

Lone pair–lone pair repulsion is greater than lone pair–bond pair repulsion, which is greater than bond pair–bond pair repulsion:
lp-lp> lp-bp > bp-bp.

Question 34

Define ‘electronegativity’.

Answer 34

Electronegativity is the power of an atom to attract the pair of electrons in a covalent bond.

Question 35

The electron distribution in a covalent bond between elements with different electronegativities will be _________.

Answer 35

The electron distribution in a covalent bond between elements with different electronegativities will be unsymmetrical.

Question 36

Order the strength of all IMFs

Answer 36

Strength: H-bonds > permanent dp-dp > vdWs’

Question 37

Which IMF is present between ALL molecules?

Answer 37

van der Waals’ forces

Question 38

Synonyms for van der Waals’ forces?

Answer 38

van der Waals’ forces/Dispersion forces/London forces

Question 39

How do you draw/display the different IMFs?

Answer 39

All dashed lines!

Question 40

What happens to the IMFs between H2O molecules when ice is formed, and at what temperature?

Answer 40

Below 4degrees C, molecules of H2O orientate themselves to form as many hydrogen bonds as possible. This causes ice to have a regular lattice structure with gaps between water molecules, meaning ice has a lower density than liquid water.

Question 41

Why does hydrogen bonding occur? x4

Answer 41

• Hydrogen is covalently bonded to a very electronegative element: oxygen/fluorine/nitrogen.
• This atom pulls the covalently bonded electron pair closer to its nucleus, and away from the hydrogen atom.
• The hydrogen atom is then left with a bare nucleus, a partial positive charge and a very high charge density (due to its very small size).
• This results in a hydrogen bond between the hydrogen and a lone pair on a neighbouring oxygen/fluorine/nitrogen atom.