Chemistry 2A/B Topic 4 Groups in the Periodic Table

Metals are on the left and the middle of the periodic table. They cover most of the table, the only elements that are non-metals are on the far right. The transition metals are in the centre block.

Transition metals have similar properties.They are responsible for hair dyes, the colours in gemstones and the colours in pottery glazes.

Metals' properties are due to the special type of bonding. They consisit of a regular arrangement of atoms held together with metallic bonds. These bonds give the metal a giant structure consisiting of positive ions and free electrons. This is because metallic bonds allow the outer electron(s) to become delocalised. This creates a 'sea' of delocalised electrons which results in many of the metals properties. The giant metallic structure and strong bonds mean that they have extremely high melting and boiling points and are insoluble. They also allow the layers of atoms to slide over eachother resulting in metals being malleable. They also conduct electricity very well.

Alkali metals are soft and have low melting points.

They react vigorously in water and form hydroxides. The reaction makes an alkaline solution.

As you go down group 1, the lone electron is in a shell that's further from the nucleus. As they're further apart, the attraction between the positively charged nucleus and the negatively charged election decreases. This means the electron is easier to get rid of. Therefore as you go down the alkali metals they become more reactive. Higher atomic number = more reactive.

Reaction with water produces hydrogen gas - they fiz on the surface. A lighted splint will indicate the hydrogen by making the notorious "squeaky pop" as the hydrogen ignites.

They all have 7 electrons in their outer shell so they have similar properties. At room temperature: Chlorine is a fairly reactive, poisonous, dense green gas , Bromine is a dense, poisonous, orange liquid , Iodine is a dark grey crystilline solid.

They react with metals to form metal halides.

They can react with hydrogen to form hydrogen halides. These are soluble, they dissolve in water to form acidic solutions.

More reactive halogens will displace less reactive ones. The higher up group 7 an element is, the more reactive it is. This is because the outer shell is nearer to the nucleus, so the pull from the positive nucleus is greater which attracts extra electrons more strongly. When halides are dissolved in water the halide ions are free to react. If a more reactive halogen reacts with a solution containing halide ions it will 'push out' (displace) the less reactive halogen.

All elements in group 0 are colourless gases at room temperature. The are inert - they don't react with much at all. The reason for this is that they have a full outer shell, they do not need to gain or lose electrons. They are all non-flammable. These properties make the gases hard to observe. They were discovered through experiments, including fractional distillation.

ARGON is used to provide an inert atmosphere in filament lamps. It's non-flammable so it stops the filament from burning away.

HELIUM is used in airships and party baloons. It has a lower density than air, so it floats.

The boiling points and densities of noble densities increase as you move down the group.