The ion of an element has $3$ positive charges. The mass number of the atom is $27$ and the number of neutrons is $14$. What is the number of electrons in the ion?

If an ion $M^{3+}$ contains $10$ electrons and $14$ neutrons, what are the atomic number and mass number of the element $M$?

$(a)$ Why did Rutherford choose gold and not any other lighter element (such as aluminium) for his experiment? Explain your answer giving two reasons.
$(b)$ Write the name and symbol of the particle chosen by Rutherford for bombardment against the gold foil in his experiment.

Electrons possess a negative charge,and protons possess a positive charge. An atom contains both,but why does it have no net charge?

Enlist the conclusions drawn by Rutherford from his $\alpha -$ ray scattering experiment.

State whether the following statement is true or false:
Atoms of a given element are identical in mass but different in their chemical properties.