Question

what is meant by valency? Write the valency of Na, Mg, Ca and Al​

Answer 1

Answer:

Combining capicity of an element is called its valency. Na =1,Mg- 2, Ca- 2,Al - 3

Explanation:

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Answer 2

Answer:

valency is the number of hydrogen atoms which can combine or displace one atom of the element to form a compound.

Extra information

valency depends upon the number of electrons in the last shell or orbit. If the electrons will be four or less than four so the valency will be positive i.e it will donate its electrons, if the number of electrons will be more than four so the valency will be negative i.e. it will except the electrons.

how to find out the no. of electrons in the last shell

for finding out the number of electrons in the last shell we have to write down the electronic configuration of the element.

For e.g. aluminium (Al) has 13 atomic number

So, we will write down the electronic configuration 2,8,3 of Al by using the formula 2n^2....in which n is the number of shell.

for 1st shell - 2n^2 = 2× 1^2 = 2×1 = 2 electrons

for 2nd shell- 2n^2 = 2× 2^2 = 2×4 = 8 electrons

for 3rd shell - 2n^2 = 2× 3^2 = 2×9 = 18electrons

but here after 1st and 2nd shell we have only 3 electrons left so the third shell will have 3 electrons.

Na has +1 valency; as it has one electron in the last shell so it will donate the electron with +1 charge.

Mg has +2 valency; as it has two electrons in the last shell so it will donate two electrons with +2 charge.

Ca has +2 valency; as it also has two electrons in the last shell so it will donate two electrons with +2 charge.

Al has +3 valency; as it has three electrons in the last shell so it will donate three electrons with+3 charge.

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