Question

(a) atom is considered electrically neutral. Explain.

(b) state the valency of helium.

(c) if an atom has atomic mass 4 and 2 protons in its nucleus. How many neutrons does it have?

Answer 1

(a).an atom is said to be electrically neutral because the positive charge is balanced by negative charge as the no.of positive charges are equal to no.of negative Charge

(b) the valency of helium is 0 but the no.of valence electrons are 2

(c). no.of neutrons=atomic mass-no.of protons
4-2=2

I hope this will help u :)

Answer 2

HI there !!

⇒AN atom consists of equal no: of protons and neutrons.

⇒Number of protons = Number of electrons

⇒Protons are positively  charged particles , whereas electrons are negatively  charged.

⇒So , the negative and positive charges balances each other

⇒Hence , when the protons and electrons are equal in magnitude , the atom as a whole is electrically neutral.

======================================

Helium:-

Atomic number = Z = 2

Number of protons = Atomic number = 2

No: of protons = No: of electrons


No: of electrons = 2

Electronic configuration = 2 , 0

Valency = No : of electrons in the valence shell = 0

Valency = 0

========================


Atomic mass = Number of protons +  Number of neutrons 
                   

Atomic number = 4

 Number of protons = 2

NO: of electrons = Atomic number - No : of protons 
                       = 4 - 2 
                      =  2 neutrons