2.5 understand that nobel gases (group 0) are a family of inert gases and explain their lack of reactivity in terms of their electronic configurations

Nobel gases (group 0, the last column in the Periodic Table) are inert, this means they don't react with many things at all. This is because the noble gases have a full outer shell, so they have no need to gain or lose electrons.

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

Elements in the same group have the same number of elements on their outer shell and therefore have similar chemical properties.

E.g all elements in group 2 have 2 electrons on their outer shell, so they all want to lose 2 electrons. Similarly, all noble gases (group 0) have a full outer shell so are inert as they don't want to lose any electrons.

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

Elements are classified as metals if they conduct electricity (because they allow a charge to pass through them easily). Metal oxides are basic, meaning they will neutralise acids, if metal oxides dissolve they will form a solution with pH of more that 7.

Elements are classified as non-metals if they are poor conductors of electricity. Non-metals are acidic and, if they dissolve, they will form a solution with a pH of less than 7.

2.2 recall the positions of metals and non-metals in the periodic table

Kind of imagine a staggered line across the table. Any element left of the line is metal, anything right is non-metal, like this...

2.1 understand the terms group and period

Groups
A group is a column in the periodic table. All elements in a group have similar chemical properties (because they have the same number of electrons on their outer shell), however, the properties of each element (such as reactivity) often gradually change as you go down a group (as the atomic number increases).

Periods
A period is a row in the periodic table. Properties of elements in the same period are not similar and quite often change.