We have just covered some fairly advanced stuff - constructing the foundation of chemistry. The table we have just produced is a basic version of the Periodic Table of the Elements.

The columns represent the number of electrons in the outer shell (from 1 to 8) and are called GROUPS. Elements in the same GROUP will have similar properties.
Each row represents a new shell of electrons, (notice: each new row is the start of a new shell once the previous shell is full). Rows are called PERIODS.

So using this convention we can say that Lithium (Li) is in Group One, Period Two.

We can guess the characteristics that an element might have by its group and period, and also pair elements together that are likely to produce strong reactions.

Remember Sodium (Na: Group 1) and Chlorine (Cl: Group 7) reacting violently when Na gave one electron to Cl to form an ionic bond?

We can predict that the other members of Group 1 - Lithium (Li), Hydrogen (H), and Potassium (K) will also react well with Chlorine (Cl) as they too want to get rid of one electron from their outer shell. For the same reason other members of Group 7, that want to find an extra electon for their outer shell will react well with Sodium (Na) - so Fluorine (Fl) will react well.

Group 1 elements with one electron to spare will always react well with group 7 elements that need an additional electron.

We can also go one step further, and predict how violent a reaction might be.

We know that it is the attraction between the negative electrons and the positive protons in the nucleus that keep the atom held together. So it makes sense that the further away the electrons are from the protons in the nucleus, the weaker the attractive forces will be between them.

Electrons very close to the nucleus in shell 1 (period 1 elements) will be held strongly, electrons far away in shell 3 or 4 (periods 3 and 4) will be held quite weakly.

Lets think about the reactions between group 1 and group 7 again. The element in group one needs to give away one electron. The element in group 7 needs to attract one electron.

It makes sense that Hydrogen (H) with its electron close to the nucleus in shell 1 will find it hard to give that electron away, as the attraction between the negative electron and the positive nucleus will be strong.

Lithium (Li) holds its single electron further away in shell two - further from the positive nucleus. The attraction will be weaker, and Lithium will find it easier to give away this electron, and should be more reactive.

Sodium (Na) with its single electron even further away in shell 3 should find it easier still and be more reactive again. Potassium (K) with the electron in shell 4 will have significantly weaker forces to overcome to give away its electron, and be very reactive.

From this we can deduct that the attractive forces in shell 1 are greater than in shell 2, those in shell 2 are greater than in shell 3, and so on.

So - it also makes sense that Fluorine will attract an electron into shell 2 more strongly than chlorine attracting the electron into shell 3, as the attraction in shell 2 is stronger than shell 3.

Group one elements will be more reactive as we move down the periods (from row to row, shell to shell), because the electron attraction gets weaker and it is easier to give electrons away.
Group seven elements will be more reactive as we move up the periods, as the electron attraction is stronger in shells closer to the nucleus, and they can pull electrons with more force.

So to test this theory we can predict that a reaction between Potassium (K) and Fluorine (F) would be particularly violent, as it is very easy for Potassium to lose its electron from shell 4 where the attraction is weak, and Flourine will attract that electron rapidly into shell 2 where the attraction is strong.

This is indeed true. Potassium (K - Group 1, Period 4) finds it easy to lose this outer electron from shell 4, and Fluorine (F -Group 7 Period 2) attracts the electron strongly into shell 2. This reaction is very, very violent.

Finally (at last - phew !!) - it is worth making clear that we cannot create or change elements. We don't have the ability to add and subtract protons from the nucleus (as you might have thought when we were drawing them here). Elements occur naturally, and while we can react them together to form compounds, we don't change them. If we could add protons to the nucleus we would be able to change Lead (82 protons) into Gold (79 protons) by taking three protons from its nucleus. If anyone finds out how to do this - please let me know.