2.5 understand that the noble gases (Group 0) are a family of inert gases and explain their lack of reactivity in terms of their electronic configurations.

Nobel gasses are inert, this means they do not react. The reason for this is because they are stable: meaning they have a full outer shell, so they do not need to loose or gain electrons.

2.4 understand why elements in the same group of the Periodic Table have similar chemical properties

Elements in the same group have the same number of electrons on their outer shell.
This means they will behave in a similar way; they will react and bond similarly.

For example in group one, the elements all form +1 ions as they each loose one electron to become stable (to have a full outer shell).

2.3 explain the classification of elements as metals or non-metals on the basis of their electrical conductivity and the acid-base character of their oxides

Metals are all conductors. Metals form metal-oxides which are alkaline.

Nonmetals don't conduct. They form nonmetal-oxides which are acidic.

2.2 recall the positions of metals and non-metals in the Periodic Table

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To the left are the metals, to the right are the nonmetals

2.1 understand the terms group and period

Groups are columns in the periodic table, the number of a group represents the number of electrons on an atom's outer shell.
Periods are rows on the periodic table, the row represents the number of orbitals that a atom has.