Electronic structure

Electronic structure

1. The electrons occupy the lowest available energy levels. They fill up each shell in turn. 2 electrons go in the first (except H which only has 1), up to 8 in the second, the third shell accepts 8 electrons and if the third shell fills up, then the remaining electrons go into the fourth shell- up to calcium.

2. For elements beyond calcium the number of outer electrons is the same as the group number. The number of outer electrons detemines the reactivity of an element.