Groups in the periodic table

What are the alkali metals?

Group 1 of the periodic table

What are the physical properties of alkali metals compared to typical metals?

Similarities:

• They are good conductors of heat and electricity

• Shiny when freshly cut

Differences:

• Alkali metals are soft (you can cut them with a knife)

• Alkali metals have relatively low melting points (but are all solid)

What do alkali metals produce when they react with water?

They produce an alkaline metal hydroxide and hydrogen. For example:

sodium + water → sodium hydroxide + hydrogen

How does reactivity differ between the alkali metals?

The reactivity of the metals increases down the group

How do lithium, sodium and potassium act when put into water?

• Lithium fizzes steadily

• Sodium melts into a ball from the heat released in the reaction, fizzes rapidly and moves around

• Potassium gives off sparks and the hydrogen produced burns with a lilac-coloured flame

What are the halogens?

Group 7 of the periodic table

What states are fluorine, chlorine, bromine and iodine at room temperature?

• Fluorine and chlorine are gasses

• Bromine is a liquid

• Iodine is a solid

What are the colours of fluorine, chlorine, bromine and iodine?

• Fluorine- pale yellow

• Chlorine- yellow-green

• Bromine- red-brown

• Iodine- dark grey: forms a purple vapour when heated

What do the elements fluorine, chlorine, bromine and iodine go around in?

• They go around in pairs

• They are diatomic, covalent molecules

What happens to melting and boiling points of the halogens as you go down the group?

• Melting and boiling points increase

• The intermolecular forces between molecules becomes stronger

• More heat energy is needed to overcome these forces

How are bonds overcome when simple molecular substances melt or boil?

• Weak intermolecular forces are overcome

• The strong covalent bond joining atoms in each molecules do not break

What happens to the reactivity of the halogens as you go down the group?

Their reactivity decreases

What happens when halogens react with metals?

They react to form metal compounds called metal halides. For example:

Sodium + chlorine → sodium chloride

What happens when a halogen reacts with a metal or hydrogen?

• The halogen gains one electron to fill it’s outer shell

• This is because the halogens are in group 7 so they have 7 electrons on their outer shell so they only need 1 more to fill it

Why does the reactivity of the halogens get weaker as you move down the group?

• The outer shell gets further from the nucleus

• There is more shielding by inner electrons

• The force of attraction between the nucleus and outer shell electrons gets weaker

• Electrons are gained less easily

• The elements become less reactive

Why does the reactivity of the alkali metals increase as you move down the group?

• The outer shell is further from the nucleus

• The force of electrostatic attraction between the nucleus and the outer shell gets weaker- this is because there is more shielding by inner electrons

• This makes it easier for the alkali metal to lose the one electron on it’s outer shell to a non-metal

How can a displacement reaction be demonstrated with halogens?

• Add a halogen solution to a metal halide solution, then see if the mixture darkens

• For example: when adding chlorine water to sodium bromide solution, the solution turns a red-brown colour

• This happens because the less reactive bromine has been displaced by the more reactive chlorine

• Bromine has a red-brown colour so the solution turns a red brown colour

Why are smaller volumes of dilute halogen solutions used by humans?

Because halogens are toxic

What are redox reactions?

When oxidation and reduction happens at the same time

What is oxidation and reduction

• Oxidation is when something gains oxygen and reduction is when something loses oxygen

• OILRIG- Oxidation is loss of electrons, reduction is gain of electrons

What are the elements in group 0 of the periodic table called?

Noble gases

What does inert mean?

Unreactive

What are the chemical properties of noble gases?

They are inert. They lack reactivity because:

• Their atoms have full outer shells of electrons

• They have no tendency to lose, gain or share electrons

What are the properties and uses for the noble gas, helium?

• It is inert

• Used as lifting gas in balloons and airships

• Low density

• Helium is less dense than air so the balloons and airships rise

• Helium is non-flammable so they do not ignite

What are the properties and uses for the noble gases: argon, krypton and xenon?

• They are inert

• Used as filling gas in filament lamps

• The metal filament becomes hot enough to glow

• The inert gases stop it burning away

What are the properties and uses for the noble gas, argon?

• It is inert

• Used in lightbulbs

• Used as shield gas during welding

• Argon is denser than air so it keeps air away from the metal

• It is inert so the metal doesn’t oxidise