![]() So the electrons fill the ns shell first and later they enter the penultimate (n-1)d orbital.Į.g. energy of 4s orbital < energy of 3d orbital. As we have seen in post 28, the sequence of filling the orbitals is such that the energy of the ns shell is always less than (n-1) d shell. ( Note – The outer shell/orbit of these elements consists of s and p orbitals).ġ)These elements are found in groups 3 to 12 in the periodic table.Ģ)In these elements, the penultimate(n-1) d-orbital is filled with electrons. There can be maximum 6 electrons in the p orbital and 2 electrons in the s orbital.So according to the electronic configurations given above, there can be 3 to 8 electrons in the outer shell of these elements. ![]() Group 8A ( Noble gases)- ns 2 np 6 (except Helium) Group 6A ( Oxygen family or CHALCOGENS) – ns 2 np 4 Group 5A ( Nitrogen family or PNICTOGENS)- ns 2 np 3 Group 4A ( Carbon family or TETRAGENS) – ns 2 np 2 Group 3A ( Boron family or ICOSAGENS) – ns 2 np 1 General electronic configuration of this block is –.This block has metals( e.g Lead,Aluminium,tin,bismuth), non-metals( e.g halogens,phosphorous,sulphur,carbon) and metalloids( e.g.The valence electrons occupy p orbitals i.e the last electron enters the p-orbital.īismuth 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 10 5s 2 5p 6 4f 14 5d 10 6s 2 6p 3.This block contains groups 3A to 8A(columns 13, 14, 15, 16, 17, and 18)with the exception of Helium (He is a s block element).Group 2 elements and helium – ns 2, ,where n = 2 to 7. Group 1 elements – ns 1, where n = 2 to 7. The General electronic configuration of this block is –.Alkali(Group 1) and Alkaline earth metals (Group2) and Helium are all s-block elements.There can be maximum 2 electrons in the valence shell as s-orbital can only accommodate 2 electrons in it.The valence electrons in the these elements are only in the s-orbital.The energy of the orbitals determines the sequence of filling- Lower energy orbitals are always preferred over high energy ones.The table is thus divided into 4 blocks namely – s,p,d, f blocks, depending on the occupation of the respective orbitals by the valence electrons of an element. The periodic table shows us the sequential filling of the electrons. In our 28th post, we have already introduced the concept of electronic configurations and the various rules that determine the sequence of filling of the shells and subshells, in an atom.In this post, let us examine the same topic, in relation to position of the elements in the periodic table.
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