011-40705070  or  
Call me
Download our Mobile App
Select Board & Class
  • Select Board
  • Select Class
Saarah Huda from Abu Dhabi Indian School, asked a question
Subject: Science , asked on 16/1/12

how to find valency of an element?

Swittie Dipi... From Aditya Birla Public School, added an answer, on 16/1/12
345 helpful votes in Science

Hi ,


The number of valence electrons is just how many electrons an atom has in its outer shell. It 's easy to figure out if you 've got a periodic table. (See the link to the left of this answer for a good periodic table).

 

All the elements in each column have the same number of electrons in their outer shells. All the elements in the first column all have a single valence electron (H, Li, Na, K, etc.).

 

The second column elements all have 2 valence electrons (Be, Mg, Ca, Sr, etc.).

 

Skipping over the gap, go to the Group 3 elements, which all have 3 valence electrons (B, Al, Ga, etc.).

 

The elements in the next column (C, Si, Ge, etc.) all have 4 valence electrons.

 

The elements in the next column (N, P, As, etc.) all have, yes, you guessed it, 5 valence electrons.

 

O, S, Se, and the others in this column have 6 valence electrons.

 

The halogens in the next-to-last column (F, Cl, Br, etc.) have 7 valence electrons.

The noble gases in the right-most column (Ne, Ar, Kr, etc.) all have 8 electrons in their out except for He, which only has 2 electrons.

 

If an atom is an ion, you must include the charge also:

For a positive ion, for each charge subtract one electron, *for instance, Na+ has 1-1 = 0, BUT it has 8 valence electrons because it has the same electron configuration as Ne. Just as K+ has the same configuration as Ar. Therefore, the Alkali metals will have 8 valence electrons.

 

For a negative ion, add one electron for each charge, for instance, O2- has 6+2 = 8 valence electrons




Hope this helps u.!!

cheers....!

  • Was this answer helpful?
  • 10
100% users found this answer helpful.
View More 3 Answer

EXPERT ANSWER

gupta_karuna... , Meritnation Expert added an answer, on 19/1/12
  • Valency of element is the no. of electron participating in chemical combination. 
  • Actually it is the valence shell which is involved in chemical combination. 
  • Therefore if electron present in valence shell is less than 3 than valency is directly equal to number of electron in valence shell.
  • If electrons present in valence shell are greater than three than 8- no. of valence electrons.
  • To find electrons in valence shell one should know atomic number. For eg for Al electronic configuration is 2,8,3 as atomic number is 13.  Thus valency is 3 as valence shell electron equals to three.  N electronic configuration 2,8,5 valency = 8-5 = 3.

This conversation is already closed by Expert

  • Was this answer helpful?
  • 5
100% users found this answer helpful.
Ashi Sharma From Delhi Public School, added an answer, on 17/1/12
2 helpful votes in Science

valency of a metal=no. of electrons it looses for getting noble gas configuration

whereas

valency of an non-metal=no. of electrons an shell can accomodate-no. of electrons present in that particular shell

  • Was this answer helpful?
  • 2
100% users found this answer helpful.
Swittie Dipi... From Aditya Birla Public School, added an answer, on 16/1/12
345 helpful votes in Science

Hi,

 

The number of valence electrons is just how many electrons an atom has in its outer shell. It 's easy to figure out if you 've got a periodic table. (See the link to the left of this answer for a good periodic table).

 

All the elements in each column have the same number of electrons in their outer shells. All the elements in the first column all have a single valence electron (H, Li, Na, K, etc.).

 

The second column elements all have 2 valence electrons (Be, Mg, Ca, Sr, etc.).

 

Skipping over the gap, go to the Group 3 elements, which all have 3 valence electrons (B, Al, Ga, etc.).

 

The elements in the next column (C, Si, Ge, etc.) all have 4 valence electrons.

 

The elements in the next column (N, P, As, etc.) all have, yes, you guessed it, 5 valence electrons.

 

O, S, Se, and the others in this column have 6 valence electrons.

 

The halogens in the next-to-last column (F, Cl, Br, etc.) have 7 valence electrons.

The noble gases in the right-most column (Ne, Ar, Kr, etc.) all have 8 electrons in their out except for He, which only has 2 electrons.

 

If an atom is an ion, you must include the charge also:

For a positive ion, for each charge subtract one electron, *for instance, Na+ has 1-1 = 0, BUT it has 8 valence electrons because it has the same electron configuration as Ne. Just as K+ has the same configuration as Ar. Therefore, the Alkali metals will have 8 valence electrons.

 

For a negative ion, add one electron for each charge, for instance, O2- has 6+2 = 8 valence electrons

 

 

hope this helps u.....!

cheers....!

  • Was this answer helpful?
  • 0

Popular questions from Structure of the Atom

Show More Questions