Question

1. An atom of Lithium has three protons and four neutrons in its nucleus.
(a) What is its atomic number and atomic mass?
(b) How many electrons does it have?​

Answer 1

atomic number= number of protons

lithium's atomic number=3

atomic mass= no. of protons+no. of electrons

lithium's atomic mass= 3+4=7

no. electron=no. of proton

lithium's electron=3

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Answer 2

a) Atomic number = 6; Atomic mass = 7

b) Number of electrons = 3

GIVEN:- Lithium has three protons and four neutrons in its nucleus.

TO FIND:-

(a) What is its atomic number and atomic mass?

(b) How many electrons does it have?

SOLUTION:-

• In chemistry, we know that the number of protons and the number of neutrons determine an element's mass number which means that atomic mass = number of protons + number of neutrons

• In chemistry, we know that Atomic number = Number of Proton = Number of electron

• Given that Number of protons in an atom of Lithium is 3.

Atomic number = Number of Proton = 3

Atomic mass = number of protons + number of neutrons

By putting values in the formula

The atomic mass of Lithium =

$3 + 4 = 7$

Number of electrons in Lithium = Number of Proton in Lithium = 3

Hence,

a) Atomic number = 6; Atomic mass = 7

b) Number of electrons = 3

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