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how to find valency of an element?

Asked by Saarah Huda(student) , on 16/1/12


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EXPERT ANSWER
  • 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.

Posted by Karuna Gupta(MeritNation Expert)on 19/1/12

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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....!

Posted by Swittie Dipi...(student)on 16/1/12

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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....!

Posted by Swittie Dipi...(student)on 16/1/12

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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

Posted by Ashi Sharma(student)on 17/1/12

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