Chem definitions

What is meant by ‘relative atomic mass’ (Ar) of an element?

The mean mass of an atom of an element, divided by 1/12th of the mean mass of an atom of the carbon-12 isotope

Ionisation energy

the minimum energy required to remove one mole of electrons from one mole of atoms in gaseous state

isotope

atoms of the same element with same number of protons but different number of neutrons

electronegativity

An atoms ability to attract the pair of electrons in a covalent bond

structural isomers

same molecular formula, different structural formula

stereoisomers

same structural formula, different arrangement of atoms in space

enthalpy change

heat energy change at constant pressure

enthalpy of formation

the enthalpy change when one mole of a substance is formed from its elements with all substances in their standard states and under standard conditions