Question

Chemistry help, please explain how I get these please

4. Determine how many valence electrons come from each subshell in the following atoms: Atom Pin PO O in PO Total Valence s-electrons p-electrons d-electrons f-electrons Electrons 2 6 a 2 C 2 7 2 o Ir Cf .

Answer 1

Note: I am solving this question by taking the definition of valence electron as the elctron in outermost shell only.

P in PO3-4

Here we have two atoms involved,P and O

The default oxidation state of O is O2-,So we have to find the oxidation state of P in the compund.

Let us assume that x is the oxidation state of P,overall oxidation state is -3.

by the law of conservation of charge,we could write the equation for charge balance as;

x + 4*(-2) = -3

x-8 = -3

x = +5

So the oxidation state of P in the compund is +5

The electronic configuration of P is [Ne] 3s2 3p3

electronic configuration of P5+ = [Ne] = 1s2 2s2 2p6

So the first table is wrong actually,P5+ has

valence electrons : 2 s electrons and 6 p electrons and no d and f electrons.

And the number of valence electrons,that is in the outermost shell(2nd shell) is 8.

O in PO3-4

O has an oxidation state of 2-.

electronic configuration of O : 1s2 2s2 2p4

electronic configuration of O2- : 1s2 2s2 2p6

In this part the configuration has valence electrons : 2 s electrons and 6 p electrons

Total number of valence electrons = 8

Ir

In the case of Ir the electronic configuration is [Xe] 4f14 5d7 6s2

Here the valence shell is 6th shell so as per question,only that shell can be considered.

It contains only 2 s electrons,no p,d,f electrons.

Since the valence shell is 6 th shell we will get total number of electrons as 2.

Note: I am solving this question by taking the definition of valence electron as the elctron in outermost shell only.

If you consider the electrons that takesplace in chemical reaction as valence elctron,Then

There is 2 s electrons and 7 d electrons.and a total of 9 valence elctrons.

Cf

Here also the electronic configuration of Cf is [Rn] 5f10 7s2.

Here the outermost shell is the 7th shell.It contains 2 s electrons.So the total number of valence electrons in Cf is 2.

5th shell is not the valence shell.

Note: I am solving this question by taking the definition of valence electron as the elctron in outermost shell only.

If you consider the electrons that takesplace in chemical reaction as valence elctron,Then

There is 2 s electrons and 10 f electrons and total 12 valence elctrons.

The table given is constructed as mentioned in the second case.But with the term "valence electrons" only given,the first method is the correct one,ignore the part with "Note" heading.