Question

1. derive the valency of an element having atomic number 5. 2. name the subatomic particle whose number is not same in isotopics species of an element 3. name the element which has no neutron in its atom

Answer 1

1)
Atomic no: = 5
No : of protons = 5
No : of electrons = 5

Electronic configuration = 2 ,3

Valency is the combining capacity of an element.It is determined by the no: of electrons in the valence shell.If there are more than 5 electrons in the valence shell , the electrons are gained.If there are less than 5 electrons electrons are lost.

Here in this case , there are 3 electrons in the valence shell.

So , the valency is 3 , as 3 electrons are lost here.

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2. Neutrons  are the subatomic particles  whose number is not same in isotopic species of an element.

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3.  Protium [ an isotope of hydrogen ]