chapter 7.3 - period trends in bonding and structure

Question 1

Properties of metals

Answer 1

Solids at room temperature except mercuy
Able to conduct electricity
Able to conduct heat

Question 2

What is metallic bonding

Answer 2

Each atom has donated its outer hell electrons to a shared pool of electrons which are delocalised throughout the whole structure
Th positive ions (cations) left behind consist of the nucleus and the inner electron shells
Metallic bonding is the strong electrostatic attaction between cations (fixed) and delocalised electrons

Question 3

Structure of metals

Answer 3

Billions of metal atoms are held together by metallic bonding in a giant metallic lattice

Question 4

Properties of metals

Answer 4

Strong metalic bonds
High electrical conductivity
High melting points and boiling points

Question 5

Explain the electrical conductivity of metals

Answer 5

• metals conduct electricity in solid and liquid states
• when a voltage is applied aacross a metal the delocalised electrons can move through the structure carrying charge

Question 6

Explain why most metals have high melting and boiling points

Answer 6

Strong metallic bonds strong esa attraction between delocalised electrons and cations

Question 7

Explain the solubility of metals

Answer 7

Metals do not dissolve

Question 8

What are simple covalent structures

Answer 8

In solids these molecules form a simple molecular lattice held together by weak intermolecular forces

Question 9

Which elements form giant covalent lattices

Answer 9

Boron carbon and silicon

Question 10

What is the structure of a giant covlent lattice

Answer 10

Billions of atoms held togehter by a network of strong covalent bonds to form a giant covalent lattice

Question 11

Structure of carbon and silicon

Answer 11

Group 4
Use the 4 electrons on their outer shell to covalently bond to other carbon or silicon atoms
This results in a tetrahedral structure
Bond angles are 109.5º

Question 12

Melting point and boiling points of of giant covalent lattices

Answer 12

High melting points and boiling points
Lots of energy is required to break the strong covalent bonds

Question 13

Solubility of giant covalent lattices

Answer 13

Insoluble in most solvents
The covalent bonds holding together the atoms in the lattice Argo strong to broken by interactions with solvents

Question 14

Electrical conductivity of giant covalent lattices

Answer 14

All four outer shell electrons are involved in covalent bonding so none are available for conducting electricity
However graphene and graphite conduct electricity

Question 15

Features of graphite and graphene

Answer 15

Allotrope of carbon
Only 3/4 of the outer shell electrons are involved in covalent bonding
The remaining electrons are released into a pool of delocalised electrons shared by all atoms in the structure
Contain planar hexagonal layers so are good electrical conductors
Bond angles = 120 º by electron pair repulsion

Question 16

Structure of graphene

Answer 16

Single layer of graphite
Hexagonally arranged carbon atoms linked by strong covalent bonds
Same electrical conductivity of copper and is the thinnest and strongest material ever made

Question 17

Structure of graphite

Answer 17

Parallel layers of hexagonally arranged carbon atoms linked
The layers are bonded by weak London forces
3/4 carbons electrons covalently bonded
Spare e- is delocalised between layers so electricity can be conducted as in metals

Question 18

Period trends in melting points

Answer 18

Across
Mp increases from group 1 - 4
Then there is a sharp decrease
The they stay low from 5-8
Metallic -giant - simple structures]at mp giant structures have strong forces to overcome so have high mp
Simple structures have weak forces to overcome so have lower melting points