To rank the effective nuclear charge Z* experienced by a valence electrons of a set of atoms that belong to a same period, you only need to apply the rule of trend: it increases as you move from left to right in the period.
So, lets do it for these atoms: P, Al, Si, Cl
The belong to a same period and the order is Al, Si, P, Cl (just see a periodic table). So the rank is Al < Si < P < Cl
Now, lets do it for these atoms:, Be, Ne, O, C
They belong to the second period. The order is Be, C, O, Ne
So, the rank is Be < C < O < Ne.
Answer:
56
Explanation:
The mass number of an atom is a sum of its number of protons and neutrons. Iron (Fe) has an atomic number of 26. This means that it has 26 protons. Since we know it has 26 protons and are told it has 30 neutrons. The mass number of this atom of Iron is 26+30 = 56
Hope this helped!
