Bonding and structure

Question 1

What is ionic bonding and how is it formed?

Answer 1

occurs between a metal and non-metal. Electrons are transferred from the metal to the non-metal to achieve full outer shells. As electrons get transferred, it creates charged particles (ions). Oppositely charged ions attract through electrostatic forces to form a giant ionic lattice.

Question 2

What is covalent bonding and how is it formed?

Answer 2

Forms between 2 non-metals. Electrons are shared between the 2 outer shells to form a full outer shell.

Question 3

What is metallic bonding and how is it formed?

Answer 3

Consists of lattice of positively charged ions surrounded by a ‘sea’ of delocalised electrons. This forms a strong electrostatic force of attraction between the oppositely charged particles.

Question 4

What can affect the strength of the metallic bond?

Answer 4

The greater the charge on the positive ion, the stronger the attractive force as more electrons are released into the ‘sea’.
Ions that are larger in size produce a weaker attraction due to their greater atomic radius.

Question 5

Describe the properties of giant ionic structures

Answer 5

• high mpt and bpt due to many electrostatic forces holding the ionic lattice together requiring lots of energy to overcome.
• when molten or in solution, ionic substances can conduct electricity as ions are free to move and carry a flow of charge
• brittle as when layers of alternating charges are distorted, like charges repel, breaking apart the lattice into fragments.

Question 6

Describe the properties of metallic structures

Answer 6

• good conductors as the ‘sea’ of delocalised electrons can move and carry a flow of charge
• malleable as the layers of positive ions can slide over one another. (delocalised electrons prevent fragmentation as they can move around the lattice)
• high mpt as strong electrostatic forces of attraction between the positive ions and delocalised electrons require lots of energy to overcome.

Question 7

Describe the properties of a simple molecular structure

Answer 7

• low mpt and bpt due to covalently bonded molecules are held together with weak van Der Waals forces in the structure. (little energy required to overcome)
• very poor conductors as their structure contains no charged particles.

Question 8

Describe the structure of macromolecular structures

Answer 8

• very high mpt as its giant covalent lattice structure has many strong covalent bonds which require great amounts of energy to break
• rigid due to strength of covalent lattice

Question 9

Describe the structure and properties of graphite

Answer 9

• each carbon atom is bonded to 3 other carbon in flat sheets
• can conduct electricity as the delocalised electrons (electrons not used in bonding) are released as free electrons which move between layers

Question 10

What is lone pair repulsion?

Answer 10

When lone pairs around the central atom provide additional repulsive forces which change bond angles. (2.5 degrees)

Question 11

What are the bond angles for linear shape?

Answer 11

180

Question 12

What are the bond angles for v-shaped/angular/bent shape?

Answer 12

104.5

Question 13

What are the bond angles for trigonal planar?

Answer 13

120

Question 14

What are the bond angles for triangular pyramid?

Answer 14

107

Question 15

What are the bond angles for tetrahedral?

Answer 15

109.5

Question 16

What are the bond angles for trigonal bipyramid?

Answer 16

90 and 120

Question 17

What are the bond angles for octahedral?

Answer 17

90

Question 18

Define electronegativity

Answer 18

The power of an atom to attract negative charge towards itself within a covalent bond

Question 19

Describe how electronegativity changes going across a period and down a group

Answer 19

Electronegativity increases along a period as the atomic radius decreases
Electronegativity decreases down a group as shielding increases.

Question 20

How is a permanent dipole formed?

Answer 20

2 atoms with different electronegativities forms a polar bond. the more electronegative atom draws more of the negative charge towards itself and away form other atom producing delta +ve and -ve region.

Question 21

How is a induced dipole formed?

Answer 21

electron orbitals around a molecule are influenced by another charged particle

Question 22

Order the 3 types of intermolecular forces from weakest to strongest

Answer 22

van der Waals , permanent dipole, hydrogen bonding

Question 23

What can effect the strength of van der Waals forces?

Answer 23

• Mr of the molecule. The larger the Mr of the molecule, the stronger the intermolecular forces.
• Shape. Straight chain molecules experience stronger van der Waals forces than branched chain molecules as they can line up and pack closer together. This reduces the distance over which the force acts

Question 24

How do permanent dipole intermolecular forces work?

Answer 24

Acts between molecules with a polar bond. The delta +ve and -ve regions attract each other and hold the molecules together in a lattice like structure

Question 25

What 3 elements only can form hydrogen bonds? and why?

Answer 25

Nitrogen, oxygen and fluorine (because these are the most electronegative)

Question 26

How are hydrogen bonds formed?

Answer 26

The lone pair on the atom from a bond with a hydrogen atom from another molecule.