chapter 1 definitions

proton number/atomic number

the number of protons in the nucleus of an atom and indicates the elements position in the periodic table

nucleon number/mass number

the number of protons and neutrons found in the nucleus of an atom of an element

orbital

the volume of space in which there is a 95% chance of finding an electron

isotopes

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

the first ionisation energy

the enthalpy change required to move one mole of electrons from one mole of gaseous atoms to form one mole of gaseous unipositive cations.

the second ionisation energy

enthalpy change required to remove one mole of electrons from one mole of gaseous univalent cations to form one mole of unipositive cations.