Group 2, the alkaline earth metals

AQA Alevel Chemistry Group 2, Inorganic Chemistry #not finished yet

Atomic radius and ionisation energy :

Atomic radius is a measure of the size of an atom and atomic radius increases down a group.

An example of this is calcium and magnesium. Calcium is bigger than magnesium as the outer electrons are in a new shell which is further away from the nucleus.

First ionisation decreases down a group due to greater atomic radius and increased amounts of shielding.

Structure and bonding

Group 2 elements are all alkaline earth metals so they bond metallically and have metallic structures .

They are solid at room temperature.

Melting point

• They are solid at room temperature.

• The bigger a metals cation is, the lower its melting point.

• As you go down a group, the cations in a metallic lattice are larger.

• Size of cation - the distance between nuclei and delocalised electrons.

• However, Mg does not follow that trend .

• Magnesium has the lowest melting point due to the fact it has a different crystalline structure.

The use of magnesium to extract titanium:

• Metals are dug up in compounds called ores.

• Seperating a metal from its ore is called extraction. An example of this is TiO2 ➡ Ti.

• You can extract the metals by reacting the ores with carbon.Example:

• However, this cannot happen with carbon and titanium as it produces titanium carbite which is brittle and not useful engineering material.

• Instead, we use magnesium to extract titanium .

The use of magnesium to extract titanium steps:

First step: Titanium (IV) oxide is the main ore of titanium and it is converted to titanium (IV) chloride (TiCl4) when it is heated in a chlorine gas with carbon.

Equation:

Second step: reduced by magnesium.

Eqaution:

In this process, magnesium donates electrons to titanium, which means that it is acting as a reducing agent.

This process is inefficient due to the 2 step process however titanium has a low density, high melting point and strength.