Bonding

Question 1

Ionic Bonding

Answer 1

strong electrostatic attraction between oppositely charged ions
- metal and non-metal

Question 2

Properties of ionic compounds

Answer 2

• HIgh melting and boiling points = Strong electrostatic attraction between ions, lots of energy to overcome attraction
• Only conducts when molten/dissolved as ions can move and carry a current

Question 3

Unit cell

Answer 3

simplest or smallest part of a crystal which when repeated generates a whole crystal

Question 4

Co-ordination number

Answer 4

number of the nearest neighbours that a given particle is in contact with in a crystalline solid

Question 5

Sodium chloride co-ordination

Answer 5

6:6 (each sodium ion is surrounded by 6 chloride ions )

Question 6

Caesium Chloride co-ordination number

Answer 6

8:8

Question 7

Why do caesium chloride and sodium chloride have differen structures??

Answer 7

The sodium ion is smaller than the caesium ion and will not fit into the CsCl Cube.

If the smaller sodium ion was placed inside such a cube then the chlroine ions could not physically kept apart and since these chlorine ions have the same charge then the crystal would break apart

Question 8

Covalent Bonding

Answer 8

A shared pair of electrons
- Non Metals

Question 9

What are two exceptions in covalent bonding?

Answer 9

Boron trifluoride - Boron doesnt have a full outer shell
Sulphur hexafluoride - Sulphur has too many in outer shell

Question 10

2 types of covalent structures

Answer 10

• Simple molecular lattices
• Giant covalent lattices

Question 11

Simple molecular substances

Answer 11

• Covalent bonds between atoms are strong
• Only weak intermolecular forces holding the molecules together
• Low mpts and bpts, No conduction of electricity, soft

Question 12

Giant Covalent Structure

Answer 12

• hrd, rigid very high melting and boiling points

Question 13

Diamond structure

Answer 13

• Each carbon atom covalently bonds to 4 carbon other carbon atoms

Question 14

Graphite structure

Answer 14

• Each carbon atom covalently bonds to 3 other carbon atoms
• One electron from each carbon atom is delocalised

Question 15

Structural properties of metals

Answer 15

• Carry a charge - outer shell electron are delocalised nd can move through the whole structure
• Layers of positive ions are formed surrounded by a sea of delocalised electrons
• Malleable, ductile, high mpts and bpts

Question 16

Dative covalent bond
(co-odrinate bonding)

Answer 16

A shared pair of electrons which has been provided by one of the bonding atoms only

Question 17

How can co-ordinate bonding be affected?

Answer 17

The electronegativity of the atoms

Question 18

Define electronegativity

Answer 18

the ability of an atom to attract the bonding pair of electrons in a covalent bond towards itself

Question 19

How are temporary dipoles made in HCl?

Answer 19

Chlorine is more electronegative . As a result the bonding electrons spend more time around the chlorine creating a temporary negative charge.
- The temporary dipole created at the chlorine creates an induced dipole in the neighbouring atom (Hydrogen)

Question 20

When covalent bonds become polar how are they described?

Answer 20

• said to have some ionic character as they dont share electrons equally

Question 21

Describe the 3 different polar covalent bonds

Answer 21

a) Non-polar = shared equally between 2 atoms and there is no charge
b) Polar = bonding electrons shared unequally, partially charged atoms
c) Ionic = complete transfer of electrons, full charges resulting in ions

Question 22

Intermediate Ionic Bonding

Answer 22

• ionic compounds do not always contain perfect ionic bond
• They are ionic but with a degree of co valency in their bonding

Question 23

van der Waals

Answer 23

• found in all molecules/ atoms
• Movement of electrons create a temporary dipole which induces a dipole into another molecule
• more electrons = stronger the forces

Question 24

What is a intermolecular force ?

Answer 24

Forces between neighbouring atoms

Question 25

Permanent dipole- dipole

Answer 25

• Polar molecules have dipoles, one is slightly negative and ones positive charge.
• If these dipoles arrange so that the negative region of one molecule is close the positive region of another molecule, there will be an attraction between them.
  (F,O,N,Cl,Br)

Question 26

Hydrogen Bonding

Answer 26

• The attraction between a lone pair of electrons in one molecule and a hydrogen in another molecule
• Between hydrogen and one atom with a very electronegative, negatively charged atom (F,O,N)

Question 27

What anomalous properties does hydrogen bonding lead to in water ?

Answer 27

• Ice is less dense than water
• Ice has the maximum number of hydrogen bonds, holding the molecule apart
• Water has a high surface tension as the network of hydrogen bonds on the surface are hard to break down

Question 28

Explain the VSEPR theory

Answer 28

• valiance shell electron pair repulsion theory
• electron pairs will repel eachother and arrange themselves as far away as possible to minimise this repulsion
• lone pairs of electrons present around the central atom provide additional repulsive forces, changing the bond angle and shape of the molecule

Question 29

Name all shapes and bond angles

Answer 29

2 bonded = linear= 180
2 b, 2 l = v-shaped = 104.5
3 bonded = trigonal planar= 120
3 bonded 1 lone = pyramid = 107
4 bonded = tetrahedral= 109.5
5 bonded= trigonal bipyramid= 120/180
6 b onded = octahedral= 90

Question 30

Non-polar bond

Answer 30

atoms have the same electronegativies and electrons are shared equally between them.