Question

What do you understand by valency, calculate the valency of Na, Mg ,Ca ,Li ?​

Answer 1

Answer:

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Explanation:

a) The valency of an element is determined by the number of valence electrons present in the outermost shell of its atom.The number of electrons lost or gained (or shared) by one atom of an element to achieve the nearest inert gas electron configuration,gives us the valency of the element.

b) i) Atomic number of magnesium=12

Electronic configuration is 2,8,2

A magnesium atom can lose its 2 valence electrons to achieve the inert gas electronic configuration of neon (2,8).

Therefore,valency of magnesium=2.

ii) The atomic number of sulphur=16.

electronic configuration=2,8,6.

A sulphur atom cannot lose 6 electrons to achieve inert gas electronic configuration due to energy consideration.It can gain 2 electrons to achieve the nearest inert gas electronic configuration of argon (2,8,8).

c) On going from left to right along a period (short period), the valency of elements increases from 1 to 4 and then decreases to 0 (zero).

Third Period Na, Mg, Al, Si, P, S, Cl, Ar,

Valency 1, 2, 3, 4, 3, 2, 1, 0,

d) All the elements in a group have the same valency.

Answer 2

As we know, electrons are arranged in different shells/orbits .The electrons present in the outermost shell of an atom are known as valence electrons.

$\sf\implies$ From the Bohr Bury scheme, we all know that the outermost shell of an atom can accommodate a maximum of 8 electrons.

In short ,The power of Sharing , gaining or losing electrons is known as Valency.

___________________________

$\rightarrow$ Na = 1

$\rightarrow$ Mg = 2

$\rightarrow$ Li = 1

$\rightarrow$ Ca = 2

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Let's understand how to find valency of an atom :

$\huge\sf\star$

the number of electrons gained lost or shared so as to make the octet of electrons in the outermost shell gives us directly the combining capacity of the element that is the valency .

For example:- , hydrogen / lithium / sodium atoms contain one electron each in their outermost shell therefore each one of them can lose one electron so they are said to have valency of 1

$\huge\sf\star$ if the number of electrons in the outermost shell of an atom is close to its full capacity then valency is determined in a different way .

For example :- the fluorine atom has 7 electrons in outermost shell and its valency could be 7 but it is easier for fluorine to gain an electron instead of loss in 7 electrons and its valency is determined by subtracting 7 electrons from the octet and this gives you are valency of flourine

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In short :

(1) For having valence electrons number in 1,2,3 will have vallency of number of electrons.

(2) For elements having valence electrons 4,5,6,7,8 , the vallency is number of electrons subtracted from 8.