The block of the periodic table to which an element belongs is decided by
- A. the number of shells it has
- B. its atomic mass
- C. the subshell that receives the last electron added
- D. whether it is a metal or a non metal
Explanation
Elements are assigned to the s, p, d or f block according to the subshell into which the differentiating electron enters, so groups I and II form the s block and groups III to VIII the p block. This classification explains why elements in the same block share broad chemical behaviour. Period number, by contrast, is given by the number of the outermost shell.