Atomic Number and Atomic Mass Number

Q.

An element contain 20 neutron in the nucleus and 19 electron around it. it contains______ proton and its atomic number is____________ and mass number is_____.

Q. The number of electrons in a neutral atom is equal to the ___.

1. mass number
2. atomic weight
3. valence number
4. atomic number

Q. Match the following elements with their respective atomic numbers.

1. 3
2. 8
3. 11
4. 1

Q. Proton has a charge of $\times$ ${10}^{-19}$ C

1. 1.6022
2. -1.6022
3. -9.1094

Q.

What is mass number of an element ? How is the mass number related to the protons and neutrons present in the nucleus of an atom ? Is it same as atomic number ?

Q.

The two carbon atoms represented below are isotopes:

The atoms of both isotopes have six protons.

Give one other way in which the isotopes are similar.

Q.

The mass number A of an atom is equal to the$\mathrm{\_\_\_\_\_\_\_\_\_\_\_\_}$

1. Number of electrons

2. Number of neutrons $+$ electrons

3. Number of protons $+$ neutrons

4. Number of protons $+$ electrons

Q. If ${}_{12}^{25}A$ and ${}_{18}^{40}B$ are two elements, which of the following are correct about them?

1. Mass number of B is 40
2. Mass number of A is 25
3. Mass number of A is 12
4. Atomic number of B is 18