Question

In fourth period of periodic table how many elements have one or more 4d electrons

Answer 1

In fourth period of periodic table,

There is no element having one or more 4d electron. As 4th period element will have electronic configuration as:  

Electronic configuration : 4s¹⁻² 3d⁰⁻¹⁰ 4p⁰⁻⁶.

So there the elements having 3d electrons not 4d electron. So the number of elements having one or more 4d electron is zero . As here elements are having 3d electrons not 4d.

Answer 2

Answer:

No elements

Explanation: electronic configurations of 4th period contains only 3d electrons

(Ar) 3d"1-10 4p"1-6