Question

An atom has 3 protons 4 neutrons and 3 electrons what is its atomic number,mass number and valency

Answer 1

7 atomic mass
mass no. 3
valency 1

Answer 2

Given:-

• No. of Protons $(p^+)$ = 3
• No. of Neutrons $(n)$ = 4
• No. of Electrons $(e^-)$ = 3

To Find:-

• Atomic Number,
• Mass Number &
• Valency.

1. Atomic Number:-

We know,

Atomic number = No. of Protons

∴ Atomic number of the element = 3

2. Mass Number:-

We know,

Mass Number = No. of Protons + Neutrons

∴ Mass Number = 3 + 4 = 7

3. Valency:-

We know,

No. of electrons in a shell (as prescribed by Prof. Neils Bohr) = 2n²

where,

• n = No. of shell

[An element’s nucleus is surrounded by many shells. Bohr named them as, K shell, L shell, M..., etc.]

∴ K shell = 2(1)² = 2 electrons

L shell = 2(2)² = 8 electrons,

but, no. of electrons left is 3 - 2 = 1. Therefore, the valency is (1 +).

[Positive if the number of valence electrons in between 1 to 4. Negative if between 4 to 8.]

@Imperius