Learn the basics about the periodic table, and how the elements are organised within it.
The periodic table consists of 7 rows called Periods, going across, and 18 columns, called Groups going down.
The elements in the Periodic Table are arranged according to their atomic number, which is the number of protons in their nucleus.
The Period shows the element’s electron shell that is being filled. For example sodium is in Period 3 and Group 1. So it has electronic configuration 2:8:1. Whereas chlorine which is also in Period 3 but Group 17 has electronic configuration 2:8:7. So in both cases it is the third shell that is being filled.
The group an element is in gives the number of electrons in the outer shell of an atom of that element.
Chemical reactions are to do with movement of electrons. So, as all elements in a particular group have the same number of outer shell electrons they have similar chemical reactions.
There are trends in properties across Periods.
As you look at the elements across the periodic table, from left to right across a period, the elements change from metals to non-metals. There is also a decrease in atomic radius. This is because more protons in the nucleus pull the electrons in.
Going from left to right there is an increase in the ionisation energy, that is the energy needed to remove the outermost electron. There is also an increase in electronegativity, which means the attraction of a bonded atom for the pair of electrons in a covalent bond.
There are also trends in properties as you move down a Group.
As you go down a group, the elements become more metallic. This is seen clearly in group 14 where carbon in period 2 is a non-metal and lead in period 6 is a metal.
Going down a group, there is also an increase in atomic radius, which means that an extra shell of electrons is added for each successive element.
There are three groups that are usually studied: group 1 called the alkali metals, group 7 called the halogens, and group 18 called the noble gases. As we go down the group 1, the metals become more reactive as metals react by losing electrons and it is easier to lose the outer shell electron the further it is from the positive nucleus.As we go down the group 17, the non-metals become less reactive as non-metals react by gaining electrons and the fewer shells the greater attraction for the incoming electron. Group 18 elements have a full outer shell of electrons and so are very unreactive. Their densities and boiling points increase on going down the group.
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