The mass of an atom is constituted mainly by

Fill in the blanks given below:
$(i)$ The circular path around the nucleus in which electrons revolve at high speed is called ......... .
$(ii)$ Electrons and the nucleus are held together by ......... force.
$(iii)$ The number of $P^{+}$ in the nucleus and the sum of the number of $P^{+}$ and $n^{\circ}$ in the nucleus are represented by the symbols ...... and ......... respectively.
$(iv)$ The sum of the number of $P^{+}$ and $n^{\circ}$ in the nucleus is represented by the term ...... and the symbol .... respectively.

Which one of the following pairs is not correctly matched?

Which of the following particles cannot be accelerated by an electric or magnetic field?

$A$ certain particle carries $2.5 \times 10^{-16} \, C$ of static electric charge. Calculate the number of electrons present in it.

The heaviest particle among the following is: