Name: Variation of Atomic Radius in Periodic Table
Uploaded: 2019-07-19
Duration: 4 min 6 s
Description: The atomic radius is defined as the distance between the atom's nucleus and the outermost shell. But do you know how it varies in the periodic table? Let's find the answer in this video.

Question

The valence of representative elements is either equal to the number of the valence electrons or eight minus this number. What is the basis of this rule?

Accepted Answer

The electrons present in the valence shell (outermost shell) are called valence electrons and their number determines the valency of the element. In the case of representative elements ( $s$ and $p$ -block elements) the valency of an element is equal to the number of the valence electrons or eight minus the number of the valence electrons.

The elements of groups $1, 2$ and $13$ lose $1, 2$ and $3$ electrons respectively to attain the nearest noble gas configuration. Thus, the valency of these elements is equal to the number of their valence electrons. The elements of group- $14$ have four electrons in their respective valence shells and thus attain the nearest noble gas configuration only by sharing with four more electrons of other atoms. Therefore, the valency of these elements is equal to the number of their valence electrons.

The elements of groups $15, 16$ and $17$ have $5, 6$ and $7$ electrons in their respective valence shells and hence, they acquire the valency $3 (8 - 5)$ , $2 (8 - 6)$ and $1 (8 - 7)$ respectively either by gaining or sharing of electrons from other atoms to attain the nearest noble gas configuration. Thus, the valency of these elements is equal to eight minus the number of valence electrons.

The valence of representative elements is either equal to the number of the valence electrons or eight minus this number. What is the basis of this rule?

Important Questions on Classification of Elements and Periodicity in Properties

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