Question

Do you expect Z* to be higher for a metal or for an element that forms small molecules in its standard state? Explain why.

Z* Effective charge seen by valence electron

Answer 1

No, The metal experience Lowest Z* in its standard state.
Because Zeff=Z−S,
Where Zeff is effective nuclear charge, Z is atomic number, and S is effective nuclear charge.
In a period of peridic table the metals are the ones which we see in the first two groups, i.e for example alkali and alkaline earth metals.
In a period the Z increases from Left to Right, but the shielding electrons which are in the inner shells remain same for the period,
For example in Na atom (1s2)(2s2,2p6)(3s1)

but in Cl: (1s2)(2s2,2p6)(3s2,3p5)

for both the sheilding will be S=2+2+6=10
where as Z= 11 for Na, whereas Z=17 for Cl
Therefore the Zeff=1 for Na, whereas and Zeff=7 for Cl

That is why Metals loose their electron from their standard state and form a cation,
Once metals form cation by loosing an electron, They will be having highest Effective nuclear charge as compared to others in the same period.
For example Na+ will be having highest Z_eff than N^-3 O^-2 F^-1 Ne