The shell is the path that electrons follow outside the nucleus. Shells can be considered as energy levels and the further away from the nucleus the higher in energy.
The periods of the periodic table are the rows that run from left to right in the periodic table. The elements are not arranged in these because of similar properties but because of their increasing atomic number from left to right.
Electrons exist in shells around the nucleus and have different configurations and layouts based on the element in the periodic table. Electrons are also very important in bonding.
Bonding describes how metallic and non metallic elements of the periodic table exist as elements or combined together to form new compounds with different properties.
Metallic bonding is the bonding found in metals, positive metal ions surrounded by a sea of delocalized electrons.
Atomic radius is the measure of the distance from the centre of the nucleus to the outer electron.
The nuclear charge of an atom is the measure of the effect of attraction between the protons in the nucleus and the outer electron
Ionisation energy is a measure of the amount of energy required to remove an outer electron from an atom creating a positively charged ion.
The Halogens in Group 17 are non metal elements that are diatomic and simple covalently bonded. They decrease in reactivity down the group but increase in their melting and boiling points.
Electrons are essential components of an element and decide its reactivity and bonding. They have their own unique properties known as quantum numbers which makes them all unique, existing in a number of sub orbitals around a nucleus.
The atomic radius is a measure of the distance from the nucleus to the valence electron.