Month: October 2019

The Ionisation Energy is the energy require to remove an electron from a gaseous atom or ion at stp.

There can be multiple ionisation energies, such as:

First Ionisation Energy: Energy required to remove an electron from a gaseuos atom to form a uni-positive ion.

The periodic table contains a lot of information. The numbers of the neutrons, electrons and protons can all be found using such information.

Proton Number = Atomic number

Neutron Number = Mass number – Atomic Number

Electron Number =  Atomic Number – Charge

Once the number of electrons has been established these should be drawn into shells (For information on how to place electrons into orbitals please read more in Atomic Structure).

Each shell can take up a number of different electrons, but for the intents of this chapter the first shell takes in 2 electrons, the second shell takes in 8 electrons, the third shell takes in 8 electrons and the in the fourth shell the maximum number of electrons that will be put in it is going to be 2 electrons.

For example:

Oxygen has 8 electrons, therefore these will be placed in shells as 2 in the first shell, and 6 in the second shell, being written as 2, 6.

Calcium has 20 electrons, therefore these will be placed in shells as 2 in the first shell, 8 in the second shell, 8 in the third shell and the final 2 in the fourth shell, being written as 2, 8, 8, 2.

In order to draw these atoms with electrons around them, one should draw the nucleus, either as the letter of the element or the number of protons and neutrons, and shells around it. The electrons are then depicted as either dots or crosses.

Putting Electrons in Shells

Diagonal relationship

A relationship within the periodic table by which certain elements in the second period have a close chemical similarity to their diagonal neighbours in the next group of the third period. This is particularly noticeable with the following pairs.

Lithium and magnesium:

(1) both form chlorides and bromides that hydrolyse slowly and are soluble in ethanol;

(2) both form colourless or slightly coloured crystalline nitrides by direct reaction with nitrogen at high temperatures;

(3) both burn in air to give the normal oxide only;

(4) both form carbonates that decompose on heating.

Beryllium and aluminium:

(1) both form highly refractory oxides with polymorphs;

(2) both form crystalline nitrides that are hydrolysed in water;

(3) addition of hydroxide ion to solutions of the salts gives an amphoteric hydroxide, which is soluble in excess hydroxide giving beryllate or aluminate ions [Be(OH)₄]²⁻ and [Al(OH)₄]⁻;

(4) both form covalent halides and covalent alkyl compounds that display bridging structures;

(5) both metals dissolve in alkalis.

Boron and silicon:

(1) both display semiconductor properties;

(2) both form hydrides that are unstable in air and chlorides that hydrolyse in moist air;