What is the electron configuration of an element in period 4 and spin quantum number of +1/2?
There are many examples. The easiest is potassium, K which has just 1 electron in its 4th energy level. The electron configuration of K is 1s2 2s2 2p6 3s2 3p6 4s1, where 1s2 2s2 2p6 3s2 3p6 represents the core electrons and 4s1 represents the valence electron.
The 4 quantum numbers are n, l, ml, and ms. You are asking about ms, and it can only have 2 values. It can be either +1/2 or -1/2. By convention, the value +1/2 represents the more stable spin. Electrons in the ground state of K have 4 quantum numbers defined as: 4, 0, 0, +1/2.
Hope this helps you understand better. JIL HIR
ICAST 2010 – Quantum Spinning Reels With Chris Strickland