7.3 : Periodic Trends in Bonding and Structure

Question 1

Define metallic bonding

Answer 1

The strong electrostatic attraction between cations ( positive ions ) and delocalised electrons.

Question 2

Describe the electrons in metals

Answer 2

When solid : each atom donates its negative outer shell electrons tons shared pool of electrons, which are delocalised throughout the whole structure.

Question 3

What is the structure called of atoms held together by metallic binding?

Answer 3

Giant metallic lattice

Question 4

List the properties of metals

Answer 4

Strong metallic bonds : attraction between positive ions and delocalised electrons

High electrical conductivity

High melting and boiling points

Insoluble

Question 5

Why and when can metals conduct?

Answer 5

When : both solid and in liquid state

Because : delocalised electrons can move through the structure and carry charge

Question 6

Why do metals have high melting and boiling points?

Answer 6

For most metals, high temperatures are necessary to provide the large amount of energy needed to overcome the strong electrostatic attraction between the cations and the electrons.

Question 7

Why are metals insoluble?

Answer 7

Interactions between polar solvents and its charges lead to reactions rather than dissolving.

Question 8

What is the structure of boron, carbon and silicon called?

Answer 8

Giant covalent lattice ( networks of atoms bonded by strong covalent bonds)

Question 9

What are the properties of giant covalent lattices?

Answer 9

High melting and boiling points ( strong covalent bonds )

Insoluble in most solvents ( strong covalent bonds )

Non conductors ( exceptions : graphene and graphite )

Question 10

What are some giant covalent lattices of carbon?

Answer 10

Diamond
Graphite
Graphene

Question 11

Why are graphene and graphite exceptions to the conductivity of giant covalent lattices?

Answer 11

Each bonded carbon atom has one spare electron which can move and carry charge.

Question 12

Describe the shape and bond angles of graphene and graphite

Answer 12

Planar hexagonal layers

120°

Question 13

Describe graphene

Answer 13

A single lager of graphite
Composed of hexagonally arranged carbon atoms linked by strong covalent bonds
Same conductivity as copper
Thinnest and strongest material

Question 14

Describe graphite

Answer 14

Composed of parallel layers of hexagonally arranged carbon atoms

Layers bonded by weak London forces

Bonding only uses three out of the four valence electrons. Therefore the spare electrons delocalised between layers.

Question 15

Describe the melting points across period 2 and 3

Answer 15

Increases from group 1 to group 4
Sharp decrease between 4 and 5
Stays comparatively low from 5 to 0

Question 16

Why is there a sharp decrease in melting point in periods 2 and 3?

Answer 16

Change from giant to simple molecular structures.

Giant structures = strong forces = high melting point

Simple structure = weak forces = low melting point