Question

the element with atomic no 57 ,belong to the period ,group and block of the periodic table

Answer 1

Dear student

The element with atomic number 57 is Lanthanum
it has the electronic configuration:
1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰5s²5p⁶5d¹6s²


​This element was actually present in the third group as it has three valence electrons.
Also it has 6 shells involved , so it lies in the 6th shell.
But since the elements beginning with atomic number 57 -71 [showed a charcterstic occupancy of the 4f shell, they were placed in the lanthanide series of the f-block elements.

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