Question

write An element X has 2 electrons in K shell, 8 electrons in L. shell and 5 electrons in M shell. i. Identify the element X and write the number of protons and electrons in it. [3] ii. Size of X-ion is greater than that of X atom though both contain the same number of protons. Give reason [1] c. Write down the formula of one of the compounds of phosphorus where it is in -3 oxidation state. [1]​

Answer 1

Given:

The element X has

2 electrons in the K shell

8 electrons in the L shell

5 electrons in the M shell

The size of the X⁻ ion is greater than the X atom.

To Find:

The element X ant the number of electrons and protons in it.

The chemical compound with phosphorus is in an oxidation state (-3).

Solution:

The electronic configuration of X is ( 2, 8, 5).

So, the element X = Phosphorus (P)

The number of protons in phosphorus = 15

The number of electrons in phosphorus = 15

And the size of the X⁻ ion is greater than the X atom because the additional electron in the valence shell of the ion is loosely attracted.

As for 16 electrons, there are only 15 protons.

The phosphorus has compounds in many oxidation states.

The chemical compound of phosphorus in the (-3) oxidation state is phosphine (PH₃).

Hence, element X is phosphorus with 15 electrons and protons each. And phosphine is the chemical compound of phosphorus in the (-3) oxidation state.

Answer 2

Given:

According to the question, the element $X$ has $2$ electrons in the $K$ shell, $8$ electrons in the $L$ shell, and $5$ electrons in the $M$ shell.

To find:

We have to find the number of electrons and protons in the element $X$ along with the name of the element $X.$

We also have to find the formula of one of the chemical compounds of phosphorous where it is in $-3$ oxidation state.

Solution:

• We can infer from the question that the electronic configuration of $X$ is $(2, 8, 5).$
• Therefore, the element $X$ is Phosphorous.
• In phosphorous, the number of electrons and protons is $15.$
• The formula of a phosphorous compound with $-3$ oxidation state is $PH_{3}$, Phosphine.

Hence, the element $X$ is phosphorous. It has $15$ electrons and $15$ protons. The formula of a phosphorous compound with $-3$ oxidation state is $PH_{3}$, Phosphine.

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