The periodic table

L.O.:

Use the periodic table to find: the symbol of an element, metals and non-metals, halogens and noble gases.Explain the reactivity of group 1 elements and their atomic number.Describe the noble gases as chemically inert Explain the uses of noble gases. Recall some properties of the halogens.

• Watch this clip.

What type of names can you hear?

Write down the name of some metals

As you watch this clip, think about the relationship between atomic number and reactivity within group 1.

The alkali metals become more reactive as their atomic number increases

Exothermic: a reaction that gives out heat to the

surroundings

Endothermic: a reaction that take in heat energy from the

surroundings

• As you watch this clip, pay to attention to:

The names of noble gases Their properties The trend in density.

Helium is much less dense than air and is used in balloons.

Why did helium replace hydrogen for use in balloons?

These gases are all chemically unreactive and are used in filament lamps and electric discharge tubes.

What happens if a the gas in a light bulb is replaced by air?

Group 7 – the halogensThe elements in group 7 of the periodic table, on the right, are called the halogens.

fluorine

chlorine

bromine

iodine

astatine

I

Br

Cl

F

At

Why are they called the ‘halogens’?

Halogens are very reactive non metals.

They are all toxic or harmful because they are so reactive. Before antiseptics, iodine was used to clean wounds as it is harmful to all things, including bacteria.

They are also never found free in nature because of their reactivity – they are found as compounds with metals.

These halogen-metal compounds are salts, which give halogens their name – ‘halo-gen’ means ‘salt-former’.

poisonous and smelly.

brittle and crumbly when solid

What are the general properties of the halogens?

All the halogens are:

They become darker in colour down the group:

non-metals and so do not conduct electricity

is pale yellow

is yellow-green

is grey

is red-brown

Halogens – what do they look like?

Chlorine Bromine

Iodine

What is the physical state of the halogens?

The melting and boiling points of the halogens increase down the group, as the molecules become bigger.

What is the state of each halogen at room temperature?

Halogen Relative size

Melting point (°C)

Boiling point (°C)

State

-220 -118

-101

-7

114

-34

59

184

gas

gas

liquid

solid

Melting and boiling points of halogens

Halogen vapoursBromine and iodine are not gaseous, but have low boiling points. This means that they produce vapour at relatively low temperature. They are volatile.

Bromine produces some red-brown vapour, seen here above the liquid bromine in the jar.

When iodine is heated gently, it changes directly from a solid to a gas without first becoming a liquid.This is called sublimation.

True/ False• In the periodic table columns are called families. F• Most elements are non-metals and are found to the

right. F• The transition metals are more reactive than the alkali

metals. F• Lithium is more reactive than sodium. F• Francium is the most reactive alkali metal. T• Carbon dioxide is produced when sodium reacts with

water. F

True/ False

• Noble gases become denser going down a group. T

• Neon is used in neon lights because it burns with a red flame. F

The periodic table

L.O.:

Use the periodic table to find: the symbol of an element, metals and non-metals, halogens and noble gases.Explain the reactivity of group 1 elements and their atomic number.Describe the noble gases as chemically inert Explain the uses of noble gases. Recall some properties of the halogens.