Ionic Compounds (Section 1f)

Ionic Compounds 

1.28 describe the formation of ions by the gain or loss of electrons
In order for atoms to become stable, they must have a full outer shell. To do this, they join with other atoms and either lose or gain electrons to have a full outer shell. When an atom has lost or gained electrons, it has become a charged particle, or an ion. 

1.29 understand oxidation as the loss of electrons and reduction as the gain of

electrons

Oxidation is the process of an atom losing electrons to become a positive ion (cation.) 
Reduction is the process of an atom gaining electrons to become a negative ion (anion.)

OIL RIG = Oxidation is loss, Reduction is gain. 


1.30 recall the charges of common ions in this specification

Hydrogen = H+ 
Lithium = Li+ 
Sodium = Na+ 
Potassium = K+ 

Beryllium = Be 2+
Magnesium = Mg 2+
Calcium = Ca 2+ 

Boron = B 3+ 
Aluminium = B 3+ 

Fluorine = F- 
Chlorine = Cl - 
Bromine = Br - 

1.31 deduce the charge of an ion from the electronic configuration of the atom

from which the ion is formed

The electronic configuration of the atom will tell you how many electrons it has in it's outer shell. From this, you know whether to round up or down. For example, sodium has an electronic configuration of; 2.8.1. This means that it has one electron in it's outer shell and will therefore need to get rid of one electron in order to become stable. Therefore, the electronic configuration of the sodium ion will be 2.8 and the charge will be; Na +1, as it has lost one electron and is therefore a positive ion (cation.) 

1.32 explain, using dot and cross diagrams, the formation of ionic compounds by
electron transfer, limited to combinations of elements from Groups 1, 2, 3

and 5, 6, 7
Dot and cross diagrams represent the process of two atoms bonding to form ions. One atom will have it's electrons displayed as dots, and the other as crosses so it is clear what electrons are being gained/lost in each atom.

This diagram shows what happens when sodium (Na) reacts with Chlorine (Ch) to form sodium chloride. Sodium has one electron in it's outer shell, and gives this to chlorine which has seven electrons in it's outer shell, so they both become stable. The red arrow indicates the electron that the sodium atom loses, and the chlorine atom gains. 

1.33 understand ionic bonding as a strong electrostatic attraction between

oppositely charged ions

In ionic bonding, atoms lose or gain electrons to have a full outer shell and become stable. Once an atom has lost or gained electrons, it has become an ion.One of the atoms will become a positive ion, and the other a negative. These ions will then be strongly attracted due to the electrostatic attraction between ions with opposite charges ( + and -).

1.34 understand that ionic compounds have high melting and boiling points

because of strong electrostatic forces between oppositely charged ions.

In order to melt or boil anything, heat must be applied to break bonds. The stronger the bond is, the more heat will need to be applied. Because ionic compounds have such strong bonds, a significant amount of heat is needed for them to melt or boil, hence why they have very high melting and boiling points. 

1.35 understand the relationship between ionic charge and the melting and boiling point of an ionic compound

The charges of an ion affect the strength of the ionic bonding. The higher the charge, the stronger the bond. For example, a lattice of 3+ and 3- ions will have a stronger force of attraction between them than a lattice of 1+ and 1- ions. This means that the bigger the difference in charge (the larger the numbers,) the higher the melting and boiling point of the ionic compound. 

1.36 describe an ionic crystal as a giant three-dimensional lattice
structure held together by the attraction between oppositely

charged ions

When an ionic compound is formed, the positively charged ions (cations) attract the negatively charged ions (anions) and arrange themselves into a three-dimensional lattice structure, held together by the attraction between the ions.

1.37 draw a diagram to represent the positions of the ions in a crystal of

sodium chloride.

The diagram shows the arrangement of the ions in a crystal of sodium chloride.