In the section on arranging electrons, you learnt that there is an stable configuration of number of electrons to be in the valence shell: 2 electrons if there is only 1 shell and 8 if there are other shells in the atom.
Use the applet in chemical symbols and build the following elements - Li, B, N, F, Mg and S. To each element, find the most happy state.
Always remember
1) the atoms only rearrange themselves during a reaction (i.e. conservation of number of atoms)
2) atoms bond to each other in a fix whole number ratio when forming molecules or ionic compounds
This will be discussed in greater detail in class...
Ions and molecules
Video 1
Ions & ionisation energy
Metal elements would tend to lose electrons forming cations while non-metal elements would accept electrons to form anions. The cations and anions would be attracted by electrostatic forces of attraction and exist together as an ionic compound.
​
However, this process would need energy to remove electrons from the valence shell of the metal atom first. This energy required is called ionisation energy. How much energy needed would depend on
(1) how many protons are in the nucleus attracting all valence electrons and
(2) shielding effect whereby shells of electrons between the nucleus and valence shells minimises the attraction between the protons and the valence electrons (more shells between, lesser attraction force and therefore easier to remove electrons).
Molecules (covalent compounds)
When 2 or more non-metal elements form compounds, the atoms would tend to share electrons and form molecules.