Q. 6.93 - An Introduction to General, Organic, and Biological Chemistry

Question

a. How does the octet rule explain the formation of a magnesium ion? 
 b. What noble gas has the same electron arrangement as the magnesium ion?
c. Why are Group $1A\left(1\right)$ and Group $\left(2\right)$ elements found in many compounds, but not Group $8A\left(18\right)$ elements?

Step-by-Step Solution

Answer

(a)Magnesium atom gives two electron to make valence shell octet and gain stability .

(b)Both has valence shell fully filled , hence octet is completed.

(c)Group $1,2$ elements are very reactive in nature whereas group $18$ elements are inert.

Part(a) Step 1: Given information

We have been given that,

Magnesium ion

We need to explain the formation using octet rule.

Part(a) Step2 : Explanation.

We know that atom become stable when it complete its octet .,$8$ electrons in its valence shell.

Now, in magnesium ion $2$ valence electrons must be given out so as to complete its octet . In this way, it becomes stable and formation takes place.

Part(b) Step1: Given information.

We have been given that,

Noble gas

We need to state the reason why noble gas has same electron arrangement as magnesium ion.

Part(b) Step2 : Explanation.

We know in magnesium ion $2$ valence shell electron is given out so as to obtain its octet and becomes stable.

Also, noble gases are inert in nature and stable , it has already $8$ electron in its valence shell and hence , it completed its octet.

Due to this , there electron arrangement becomes same.

Part(c) Step1: Given information.

We have been given that,

Group $1$, Group $2$, Group $18$

We need to state the reason why group $1,2$ element found in many compounds but not group $18$ element.

Part(c) Step2 : Explanation.

Group $1, 2$ elements are alkali and alkaline earth metals and they have $1$ or $2$ valence electrons which can easily given out and react rapidly, whereas group $18$ elements are noble gas which very stable in nature ,they can't react.

Therefore, due to above reason group $1,2$ elements are found in many compounds whereas group $18$ elements are not .