Periodicity of Physical Properties
- ATOMIC RADIUS ( Total distance from an atom's nucleus to the outermost orbital of electron )
It gives information about the relative size of an atom.
It decreases across the period ==> nuclear charge increases (more protons) ==> great force of attraction between the positevely-charged nucleus and the outermost electrons ==> small size
It increases as you go down a certain group ==> number of electronic shells increase ==> large atoms
- IONIC RADIUS ( Radius of an atom forming an ion or a ionic bond )
Atoms of Metallic Elements ==> Cations (smaller than their original atoms/Outer shell electrons lost) ==> increasing nuclear charge ==> greater attraction
Atoms of NonMetallic Elements ==> Anions (larger than their original atoms/One or more electrons gained) ==> more repulsion between electrons ==> constant nuclear charge ==> lower force of attraction
- FIRST IONISATION ENERGY ( Energy needed to remove one electron from an atom )
It increases across the period as the nuclear charge increases.
Periodicity of Physical Properties II
- ELECTRICAL CONDUCTIVITY ( Measure of a material's ability to accomodate the transport of an electric charge )
It increases across the Metals of Period 3 ==> delocalised electrons (free to move) ==> more electrons to make the electric charge flow through them
It decreases across the NonMetals of Period 3 ==> electrons unable to move
- MELTING POINT ( is the temperature of a solid at which changes its state from solid to liquid at atmospheric pressure )
It depends on the bond and the structure of the element.
Giant molecular structure ==> strong covalent or metallic bonds ==> higher melting point
Simple molecular structure ==> weak Van Der Waals' intermolecular forces ==> lower melting point