electronegativity - atomic theory 8

electronegativity definition

relative power of attraction an atom of an element has for the shared pair of electrons in a covalent bond

trends in periodic table in electronegativity values ?

values increase going across a period, values decrease going down a group

why does electronegativity increase going across a period

increase in nuclear charge (number of protons increases) leading to a decrease in atomic radius

why does electronegativity decrease down a group

due to the addition of extra shells making the atomic radius larger AND due to an increased screening effect of the inner completed hsells on the outer electrons

do metals or non metals tend to have higher electronegativity values

metals have low, non metals have high

how do you know which element comes first when writing formulae with ide endings

atom with the lower electronegativity value gets written first

CATION

overall positive charge

anion

overall negative charge

intramolecular

within one molecule

intermolecular

between two or more molecules

ionic bonds

formed due to the electrostatic attraction between oppositely charged ions caused by the complete transfer of electrons from one atom to another

Why are ionic compounds crystalline?

because they are made up of an orderly arrangement of oppositely charged ions which give rise to a lattice structure

Why are ionic compounds solid?

because there are extremely strong attractions between the oppositely charged ions which hold the ions tightly together giving a solid structure.

Why do ionic compounds have high boiling points/ melting points?

The extremely strong attractions between the oppositely charged ions require large amounts of energy to break

GENERAL PROPERTIES OF IONIC COMPOUNDS

• usually solid crystalline compounds

• conduct electricity when in dissolved and molten state

• dissolve/are soluble in polar solvents

• high melting and boiling points

Why are ionic compounds usually solid crystalline compounds

due to individual ions attracting other ions

why do ionic compounds conduct electricity in certain states

in the molten/dissolved state, ionic compounds conduct electricity as their ions are free to move

why are ionic compounds soluble in polar solvents

as attraction between the ions in the compound and polar water are strong enough to pull the crystalline lattice apart

ionic materials in everyday life

• washing soda crystals (Na₂Co₃) are used to soften hard water

• Aluminium sulphate is used as an agent to prepare water for drinking

• salt tablets are used to replace salt lost in sweat