The valency of an element is linked to how many electrons an atom must gain or lose to achieve the same electronic structure as a noble gas i.e., have a full outer shell. For example an element in ...

Norman Campbell discusses the problem of the possible consistency of the assumptions about the motion and arrangement of electrons in the atom underlying ... theory of atomic structure, and ...

Listen to the full series on BBC Sounds. Hans Geiger and Ernest Marsden tested the plum pudding model. They aimed beams of positively-charged particles at very thin gold foil. These particles ...