Periodic table

• The periodic table is composed of elements that are metals, metalloids and non-metals. Columns make up elements with similar properties and are known as groups. Rows make up elements with the same number of occupied energy levels and are known as periods.Blocks in the periodic table allow quick identification of highest occupied sublevel and can be used as an easy tool to identify the electron configuration of an element.Atomic radius increases down a group in the periodic table due to the increase in number of occupied energy levels, and decreases going across a period due to the increase in effective nuclear charge.Positive ions are smaller and negative ions larger than their parent ions.The general trend in ionisation energy, electron affinity and electronegativity decreases going down a group and increases going across a period.The reactivity of group 1 elements with water increases going down the group, the reactivity of group 17 elements with halide ions decreases going down the group.Metallic and non-metallic properties show a continuum, including in the acid base nature from basic metal oxides through amphoteric to acidic non-metal oxides.Oxidation states are a helpful tool to track electron distributions in a substance, pure elements have an oxidation number of zero. The periodic table is composed of elements that are metals, metalloids and non-metals. Columns make up elements with similar properties and are known as groups. Rows make up elements with the same number of occupied energy levels and are known as periods.Blocks in the periodic table allow quick identification of highest occupied sublevel and can be used as an easy tool to identify the electron configuration of an element.Atomic radius increases down a group in the periodic table due to the increase in number of occupied energy levels, and decreases going across a period due to the increase in effective nuclear charge.Positive ions are smaller and negative ions larger than their parent ions.The general trend in ionisation energy, electron affinity and electronegativity decreases going down a group and increases going across a period.The reactivity of group 1 elements with water increases going down the group, the reactivity of group 17 elements with halide ions decreases going down the group.Metallic and non-metallic properties show a continuum, including in the acid base nature from basic metal oxides through amphoteric to acidic non-metal oxides.Oxidation states are a helpful tool to track electron distributions in a substance, pure elements have an oxidation number of zero

Metals

 are elements on the left-hand side of the periodic table that exhibit the physical properties of malleability, lustre, high melting points, high thermal and electrical conductivities and have a tendency to lose electrons.

Non-metals

 are elements on the right-hand side of the periodic table that are typically brittle, dull and have lower melting points, low thermal and electrical conductivities and have a tendency to gain electrons.