Why is electron spin important when writing electron configurations? Explain in terms of the Pauli exclusion principle.
Solution 13E:The Lewis symbol for an element consists of the element’s chemical symbol plusa dot for each valence electron. (a) AlThe atomic number of Al is 13 2 2 6 2 1 2 1The electronic configuration of Al atom is 1s 2s 2p 3s 3p or [Ne]3s 3pThe number of valence electrons in Al atom is = 2+1=3 The Lewis symbol for Al is(b) BrThe atomic number of Br is 35The electronic configuration of Br atom is 1s 2s 2p 3s 3p 3d 4s 4p .or [Ar]3d 4s 4p0 2 5 10 2 5The number of valence electrons in Br atom is = 2+5=7 The Lewis symbol for Br is(c) ArThe atomic number of Ar is 18The electronic configuration of Ar atom is 1s 2s 2p 3s 3p or [Ar] 2 6 2 6The number of valence electrons in Ar atom is = 2+6=8 The Lewis symbol for Ar is(d) SrThe atomic number of Sr is 38 2 2 6 2 6 10 2 6 2The electronic configuration of Sr atom is 1s 2s 2p 3s 3p 3d 4s 4p 5s . 2or [Kr]5s .The number of valence electrons in Sr atom is = 2 The Lewis symbol for Sr is