Atomic radius Atomic radius increases down the Group. As one goes down the group, the atoms have more shells of electrons making the atom bigger. 1st ionisation energy The outermost electrons are held more weakly because they are successively further from the nucleus in additional shells. In addition, the outer shell electrons become more shielded from the attraction of the nucleus by the repulsive force of inner shell electrons 2.2 Group 2 Melting points Down the group the melting points decrease. The metallic bonding weakens as the atomic size increases. The distance between the positive ions and delocalized electrons increases. Therefore the electrostatic attractive forces between the positive ions and the delocalized electrons weaken.
3.2.2 Group 2, the alkaline earth metals
The trends in atomic radius, first ionisation energy and melting point of the elements Mg–Ba
Students should be able to:
• explain the trends in atomic radius and first ionisation energy
• explain the melting point of the elements in terms of their structure and bonding.