CIE IGCSE Chemistry Solved Past Paper May/June 2020 P42
1c) Gallium has an electron configuration of 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p1: lowest energy level is the one which is nearest to the atom’s nucleus and that is s subshell of quantum shell 1. Highest energy level is in quantum shell 4 and has p subshell with only 1 electron.
1 aiii) Ionisation energy is energy required to remove an electron from a gaseous atom’s outermost shell. When nucleur attraction increases, ionisation energy increases and nucleur attraction increases when number of electrons increase and shielding effect remains same.