Trend in Physical properties of Period 3 elements: Electronic configuration: The 3rd shell starts from sodium and completes at argon. 11Na → 1s2, 2s2, 2p6, 3s1 = [Ne], 3s1 12Mg → 1s2, 2s2, 2p6, 3s2 = [Ne], 3s2 13Al → 1s2, 2s2, 2p6, 3s2, 3p1 = [Ne], 3s2, 3p1 14Si →Trends in physical properties of elements in period 3 – Digital Kemistry