Section 2 a) Summary

This is the most widely recognised version of the Periodic Table of Elements. At IGCSE level, the transition metals are not really relevant, so we look at a version like this:

The main difference is just that the middle groups are not counted, making it easier to recognise which group each element falls into. The Periodic table is organised based on the properties of the elements. A line can be drawn from between boron and aluminium to between polonium and astatine to separate metals and non-metals. The left side, and the majority of the table, is classified as metals. The right is non-metals.
Metals are characterised by:

• Basic (Alkali) hydroxides
• Electrical and heat conductivity
• Giant metallic structure/metallic bonds
• Ability to form cations

Non-metals are characterised by:

• Acidic hydroxides
• Insulating properties (except carbon)
• Covalent bonding
• Ability to form anions

Group 1 - Alkali metals
The first group is the alkali metals. They each have 1 valence electron. Reactivity increases as the periods increase, because the outer shells increase in distance for the nucleus and the forces of attraction weaken, so the element is able to lose this electron more easily.

Alkali metals react with cold water, an indication that they are extremely reactive.
Lithium, Li: Vigorous reaction, gives off bubbles of hydrogen gas, floats on the surface until the product created dissolves.
Sodium, Na: Faster, more vigorous reaction than lithium, melts into a sphere and lets off some yellow sparks.
Potassium, K: Violent reaction, creates a purple flame and pops with the force of hydrogen production.
The larger elements; Rb, Cs and Fr react so violently that it is unsafe to have in a school - they combust and create large explosions.
They also decrease in melting and boiling points as the atoms increase in size.

Group 7 - Halogens
Halogens are the seventh group of elements. They are non-metals that exist naturally as diatomic molecules. They each have 7 valence electrons; one short of a full outer shell. They all have antimicrobial properties in small quantities, but in large doses they are extremely toxic.

Halogens react with iron wool:

And with hydrogen gas:

As they become larger (descend down the periods?), Halogens become less reactive, darker in colour, more dense, and have a higher melting and boiling point.


Group 0 - Noble gases
Noble gases are the last group of the periodic table. Each of the elements has a full outer shell of electrons, so they are inert. Noble gases are the only elements that can form stable single-atom molecules at room temperature and pressure.
Noble gases include: Helium, neon, argon, krypton, xenon and radon.