why the lanthinoids and actinoides does not have 1 e- in thier f subshell as after filling of the 2e- in the s subshells they should have 1e- in the f subshell and the f block series should start from them but it do not starts tell the reason why this happens and also tell me the reason behind anamalous configuration of these 2 elements

Dear Student,

In Lanthanum and Actinium, the electron goes to d orbital and not f-orbital. 
This is necause, initially the energy of 5d is less than 4f. But once one electron is filled in 5d, then the energy of 5d increases and now 4f orbital energy decreases. Now, the electrons starts filling in 4f instead of 5d. 

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The main reason is that the f-block elements have poor shielding effect due to which the these elements have lanthanoid contraction
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