Write two differences between isobars and isotopes.

Write the names of three elementary particles which constitute an atom. Which of these particles determine the mass of an atom? Justify your answer with an example.

State whether the following statement is true or false:
One atomic mass unit is a mass unit equal to exactly one-twelfth $(1/12)$ the mass of one atom of carbon-$12$.

Differentiate between atomic mass and mass number.

$(a)$ Write the names of three isotopes of hydrogen.
$(b)$ State one use of an isotope of uranium.
$(c)$ Isotopes of an element have similar chemical properties. Why?

Rutherford's $\alpha$-particle scattering experiment showed that:
$(i)$ electrons have negative charge
$(ii)$ the mass and positive charge of the atom is concentrated in the nucleus
$(iii)$ neutron exists in the nucleus
$(iv)$ most of the space in the atom is empty
Which of the above statements are correct?