Electronegativity is the ability of an atom to attract bonding electrons in a covalent bond
Across a period, nuclear charge increases and atomic radius decreases, meaning a stronger attraction between the nucleus and electrons, so electronegativity increases
Down a group, the atomic radius increases and shielding effect increases, meaning a weaker force of attraction between the nucleus and electrons, so electronegativity decreases
Polarising power is the ability of a cation to distort an electron cloud
Polarisability is how easy it is for an anion's electron cloud to be polarised
Bond polarity is the distribution of electric charge across a bond
Polar bonds are an uneven distribution of electric charges in a covalent bond
Non-polar bonds are an even distribution of electric charges in a covalent bond
The larger the difference in electronegativity, the more polar the bond