Name: Need for Classifying Elements
Uploaded: 2019-07-19
Duration: 8 min 18 s
Description: We all like things that are properly arranged and placed. What about the arrangement of elements? On what basis can they be arranged? Let us explore.

Question

Complete the following table using the periodic table.

Period number	Total number of elements	Elements from	Elements To	Total number of elements in s-block	Total number of elements in p-block	Total number of elements in d-block	Total number of elements in f-block
$1$
$2$
$3$
$4$
$5$
$6$
$7$

Accepted Answer

The first period starts with K-shell which contains only one sub-shell, the ( $1 s$ ). For this subshell only two types of electronic configurations are possible and they are $1 s^{1}$ ( $H$ ) and $1 s^{2}$ ( $He$ ).

Second period starts with the 2nd main shell (L) which has two subshells, namely, $2 s$ and $2 p$ . Eight types of configurations are possible in this shell (L). Hence the second period contains 8 elements $Li, Be, B, C, N O, F$ and $Ne$ .

Third period starts with third main shell (M) which has 3 subshells, namely, $3 s, 3 p$ and $3 d$ . Therefore, the third period contains again 8 elements, which includes two s-block elements ( $Na, Mg$ ) and six p-block elements ( $Al to Ar$ ).

Fourth main shell (N). This shell (N) has four sub-shells namely $4 s, 4 p, 4 d$ and $4 f$ . The fourth period contains 18 elements which include two s-block ( $K, Ca$ ), 10 elements from d block ( $Sc to Zn$ ) and six elements from p-block ( $Ga to Kr$ ).

On the same lines, we can explain why there are 18 elements in the fifth period ( $7$ ). There are thirty two elements in the Sixth period from $Cs to Rn$ .

Seventh period is also contain 32 elements and contains 2 elements from s-block ( $7 s$ ) 14 elements from f-block ( $5 f$ ), 10 elements from d-block ( $6 d$ ) and six elements from p-block ( $7 p$ ).

Period number Total number of elements Elements from Elements To Total number of elements in s-block Total number of elements in p-block Total number of elements in d-block Total number of elements in f-block

$1$ $2$ $H$ $He$ $2$ - - -

$2$ $8$ $Li$ $Ne$ $2$ $6$ - -

$3$ $8$ $Na$ $Ar$ $2$ $6$ - -

$4$ $18$ $K$ $Kr$ $2$ $6$ $10$ -

$5$ $18$ $Rb$ $Xe$ $2$ $6$ $10$ -

$6$ $32$ $Cs$ $Rn$ $2$ $6$ $10$ $14$

$7$ $32$ $Fr$ $Og$ $2$ 6 10 $14$

Element	Valence electrons	Group number	Period number
Sulphur
Oxygen
Magnesium
Hydrogen
Fluorine
Aluminium

Elements	Group / Period / Neither group nor period
$Li, C, O$
$Mg, Ca, Ba$
$Br, Cl, F$
$C, S, Br$
$Al, Si, Cl$
$Li, Na, K$
$C, N, O$
$K, Ca, Br$

Telangana Board Solutions for Chapter: Classification of Elements-The Periodic Table, Exercise 1: Exercise 1

Telangana Board Physical Science Solutions for Exercise - Telangana Board Solutions for Chapter: Classification of Elements-The Periodic Table, Exercise 1: Exercise 1

Questions from Telangana Board Solutions for Chapter: Classification of Elements-The Periodic Table, Exercise 1: Exercise 1 with Hints & Solutions

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