Meaning of atomic number

Q. EAN of a central atom in a complex = Atomic number of the central atom (Z) - (oxidation number of the central atom with sign) + number of electrons collected from the ligrands. What is the meaning of "number of electrons collected from the ligrands"?

Q. In a radioactive disintegration , the ratio of initial number of atoms to the number of atoms present at an instant of time equal to its mean life is

Q.

The phrase "periodicity in the properties of elements” means that when elements are arranged in the increasing order of their atomic numbers, similar elements

Q. Two gases-argon $($atomic radius $0.07\text{nm}$, atomic weight $40)$ and xenon $($atomic radius $0.1\text{nm}$, atomic weight $140)$ have the same number density and are at the same temperature. The ratio of their respective mean free paths, is closest to: