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.

Section 2 a) Key Words

Acid: A substance with a low pH (less than 7). The lower the pH, the more acidic (due to more H+ ions). Can neutralise bases and form salts.

Alkali metals: Metals in group 1 of the periodic table; they have 1 valence electron. They are highly reactive and form very strongly basic hydroxides.

Base: A substance with a high pH (more than 7). The higher the pH, the more basic (due to more OH- ions). Also known as alkalies, they can neutralise acids and form salts.

Diatomic molecules: Molecules that are comprised of two atoms.

Group: The columns of the periodic table. Elements of the same group have the same number of valence electrons.

Halogens: Elements in the 7th group of the periodic table. They have seven valence electrons, and are all non-metals, whose hydroxides are strongly acidic.

Inert: A substance that does not react. Noble gases are unreactive, therefore they are inert.

Metal: Elements that conduct electricity and heat, and whose hydroxides are basic. They bond together in a giant metallic crystal, with a sea of free electrons.

Noble gas: An element in the last group of the periodic table, group 0 or group 8. It is inert, and has a full outer shell of electrons

Non-metal: Elements that generally do not conduct electricity (carbon is an exception). Form covalent bonds involving a shared pair of electrons, and their hydroxides are acidic.

Period: The rows of the periodic table. Indicates how many shells of electrons there are.

Periodic table: A table of organisation for the chemical elements, developed by Mendeleev  (though not quite as we know it today, and there are many other versions)

Valence electrons: Outer-shell electrons

Section 2 a) Specification

2.1 understand the terms group and period 

The period is the row that the element is in, it indicates how many shells of electrons it has.

The group is the column in which the element can be found. It indicates how many valence electrons the element has.

2.2 recall the positions of metals and non-metals in the Periodic Table 

The non-metals lie to the right of the red line, and metals to the left:

2.3 explain the classification of elements as metals or non-metals on the basis of their electrical conductivity and the acid-base character of their oxides 

Metals are characterised by their conductive abilities, and that their oxides dissolve in water to form bases.
Non-metals are insulators (except for carbon), and their oxides dissolve in water to form acids.

2.4 understand why elements in the same group of the Periodic Table have similar chemical properties 

Elements in the same group have the same number of valence electrons: they have to gain or lose the same number of electrons. This means their chemical properties are similar, but as the periods change the characteristic gradually changes. (e.g. reactivity increases, the colour gradually darkens, etc.)

2.5 understand that the noble gases (Group 0) are a family of inert gases and explain their lack of reactivity in terms of their electronic configurations.

Noble gases have full outer shells, so they are unreactive. Reactive elements are unstable, and react to achieve a full outer shell, but because noble gases have full outer shells, they don't have electrons to gain or lose.