Unit 2: Chapter 1 - Structure and Bonding

Question 1

Chemical Bonding

Why are metals positive charged ions in ionic bonding?

Why are non-metals negatively charged ions in ionic bonding?

How do we draw ionic bondings in electron diagrams?

Answer 1

A compound contains two or more elements that are chemically combined together.

LOSING ELECTRONS TO FORM POSITIVE IONS

In ionic bonding, metals often lose electrons to form positively charged ions. Ions have electronic structure of a noble gas.
e.g. Na (2,8,1) -> (2,8)

(2,8) is the electronic structure of neon. However it has one proton in the nucleus than there are electrons in around the nucleus. So this is why Na is Na+.

GAINING ELECTRONS TO FORM NEGATIVE IONS.

Similarly a non-metal gains an electron which is one more than the protons in the nucleus. This is why it is negatively charged.

You need to put brackets around the electron diagram with the ion symbol outside it. e.g.

[Cl] -
[Na] +

Question 2

Ionic Bonding

What is the arrangement of ions in ionic bonding?

What is the force between the ions called?

Why is the force so strong?

Answer 2

Ionic bonding is held together by electrostatic forces of attraction.

The ionic bonding results in a arrangement of a GIANT LATTICE.

The force exerted on an ion on other ions is exerted equally which is why the giant structure is held so strongly.

Question 3

Formulae of Ionic Bondings

In terms of charges, what is the general rule used in ionic bonding?

Answer 3

The charges on the ions always cancel each other out.

e.g. Na(+) + Cl(-) -> NaCl

Ca(2+) + Cl(-) -> CaCl2

MORE COMPLICATED IONS

Some ions are made up of more than one element. Eg carbonate ions (CO3) which is 2-. This can react with Ca(2+) to produce CaCO3.

The rule about cancelling charges applies here too.

Hydroxide OH (-) 
Nitrate NO3 (3-)
Carbonate CO3 (2-)
Sulfate SO4 (2-)

Question 4

Covalent Bonding

What is covalent bonding?

What is are giant covalent structures?
Give examples of giant covalent structures?

Answer 4

Non-metals reacting together is by covalent bonding.

SIMPLE MOLECULES

This is the sharing of electrons to fill the outer shell of an atom.

Sometimes an atom will need several atoms fill the outer shell such as CH4.

GIANT COVALENT STRUCTURES

Many substances containing covalent bonds consist of small molecules, such as H2O.

Some giant structures are arranged in a network of covalent bonds and are sometimes referred to as MACROMOLECULES.

For example, diamond and silicon dioxide have a giant covalent structure. This results in a GIANT COVALENT LATTICE.

Question 5

Metals

What causes the metals to form crystals?

What are ‘sea’ of electrons known as?

What is force that holds the positive ions and negative ions.

Answer 5

Metals are arranged in regular rows and forms crystals.

METALLIC BONDING

The outer electrons of a metal atom can easily move throughout the giant structure. The electrons in the highest energy level form a ‘sea’ of electron. Strong electrostatic attraction between the positively charged ions and negatively charged electrons. The electrons act as glue.

The ‘sea’ of electrons are called DELOCALISED ELECTRONS. They are no longer linked to a particular ion in a giant metallic structure. These electrons help us explain their properties.