Ionic Bonding

When beginning to learn the important concepts and knowledge required to engage with the DP Curriculum it is important to have a basic understanding and experience of some of the ideas in each topic. At AIS the majority of students follow the iGCSE Coordinated Science curriculum as a precursor to studying DP chemistry and this site will use some of the objectives from the iGCSE to provide an area of prior learning - allowing those students who would like to refresh their knowledge or for new students to engage wth matter that has become prior to starting this course.

To this end students are expected to have a basic understanding of the C3 Atoms, elements and Compounds with the direct aim of constructing formula for common elements and compounds and balancing symbol equations.

Constructing Formula for Common Elements and Compounds

Constructing Ionic Formulae

In earlier chemistry you will have learned that:

• All Atoms are made of Protons (positively charged) and Neutrons (no charge) and that these are found in the Nucleus
• You cannot change the number of protons as this will change the element (as an example an element with 8 protons is Oxygen - but 9 is Fluorine)
• Around the outside of the Nucleus tiny negatively charged particles called ELECTRONS orbit the nucleus (kind of like how planets orbit the Sun)
• A neutral atom contains the SAME NUMBER OF PROTONS and ELECTRONS

You may also have learned that:

• Atoms can GAIN or LOSE ELECTRONS
• When they gain electrons they become NEGATIVELY CHARGED
• When they lose electrons they become POSITIVELY CHARGED
• Each row in the Periodic Table is called a Period and represents a 'Shell' of electrons
• All atoms want to have a FULL SHELL OF ELECTRONS and will happily lose or gain electrons in order to have a full shell - this is called the STABLE OCTET RULE
• When Atoms lose or gain electrons they become CHARGED PARTICLES
• Charged Particles are called IONS

Here you can see that the outer electron of Sodium transfers to the outer shell of Chlorine

Forming a Positive Sodium Ion and a Negative Chloride Ion

In the below diagram - you can see that these ions Attract each other (shown by the squiggly lines) - these attractions are called Ionic Bonds

Properties of Ionic Substances

Melting and Boiling Points/ State of Matter

Ions in Ionic Formula are Oppositely Charged - and thus are Strongly Attracted to each other

However Only Opposites Attract and so the Ions Arrange themselves in a Regular Order (+ - + - + - etc) of repeating Positive and Negative ions. as these repeat again and again - in the millions of atoms they form a 3 Dimensional cube (like the picture below) that is huge. This means that one ion will have the opposite ion Above, Below, to the left, to the right, in front and behind. This means that Ionic Lattices have Many Strong ELECTROSTATIC ATTRACTIONS.

These strong Electrostatic Attractions require huge amounts of energy to separate and so..

Ionic compounds tend to have High Boiling Points and Melting Points and due to this are SOLID at room temperature