Question

Taking the example of an element of atomic number 10 explain how the electronic configuration of an atom of an element relates to the position in the modern periodic table and how valency of an element is calculated on the basis of their atomic number

Answer 1

$\bold{MODERN \: PEROIDIC \: TABLE}$

$\large{ \begin{tabular}{|c|c|c|c|c|c|c|c|} \cline{1 - 8} H_1& & & & & & & He_2 \\ \cline{1 - 8} Li_3&Be_4&B_5&C_6&N_7 &O_8&F_9& Ne_{10} \\ \cline{1-8} \end{tabular}}$

Above are first ten elements of modern periodic table.

$\bold{ELECTRONIC \: CONFUGURATION}$

Electro configuration means placing fixed number of atoms in shells .
The number that are contained in shell are according to $2^{n}$ , which is the maximum number of electron that element can have in that shell.

Where n is an integer.

For Neon (Ne)

Atomic number = 10

So, for first shell

K = $2^{1}$

K = 2

So, first shell or K shell of Neon can have only 2 electrons.

L = $2^{2}$

L= 8

So, second shell or L shell of Neon can have only 8 electrons and the atomic nunber gets equally divded.

Hence, the electronic configuration of other elements will be,

$\begin{tabular}{|c|c|} \cline{1-2} H&(1) \\ \cline{1-2} He&(2) \\ \cline{1-2} Li&(1,2) \\ \cline{1-2} Be&(2,2) \\ \cline{1-2} B&(2,3) \\ \cline{1-2} C&(2,4) \\ \cline{1-2} N&(2,5) \\ \cline{1-2} O&(2,6) \\ \cline{1-2} F&(2,7) \\ \cline{1-2} Ne&(2,8) \\ \cline{1-2} \end{tabular}$

All elements are in need to be stable like nearest noble gas , so they either loses or gains electrons to be stable.

Hence, the valency will be
elements will be,

$\begin{tabular}{|c|c|} \cline{1-2} H&+1 \\ \cline{1-2} He&0 \\ \cline{1-2} Li&+1 \\ \cline{1-2} Be&+2 \\ \cline{1-2} B&+3 \\ \cline{1-2} C&-4\\ \cline{1-2} N&-3 \\ \cline{1-2} O&-2 \\ \cline{1-2} F&-1 \\ \cline{1-2} Ne&0 \\ \cline{1-2} \end{tabular}$

◼In a period ,elements have valency increasing by one for metals till valency +3. The decreases for the non metals.
And number of peroid states number of shells.

◼In a group valency remains same while number of shell increases by one and valency states group number.

So, if an element lets say X have atomic number 12 , its

Electronic configuratkon will be (2,8,2)

Valency will be +2

Since the number of shells is 3 , therefore it lies in period 3 .

Since the valency is +2 it lies in group 2 of modern peroidic table.