Question

An element has 4 protons, 5 neutrons & 4 electrons.
1. What is its atomic no?
2. What is the mass no?

Answer 1

Answer:

beryllium and mass>9.012182 u

Answer 2

Atomic number = 4; mass number = 9

Explanation:

Given:

An element has 4 protons, 5 neutrons and 4 electrons.

1) Atomic number = number of protons or electrons = 4.

2) Mass number = numer of protons +  number of neutrons = 4 + 5 = 9.

The element has atomic number 4 and mass number 9. From the periodic table, we can infer that the element with the given property is Beryllium (Be).