Fluoride ion $(F^-)$ is isoelectronic with:

The ratio of the number of neutrons in $_6C^{12}$ and $_{14}Si^{28}$ is ....

Match the following species with their respective number of electrons:
| Species | Number of electrons |
| :--- | :--- |
| $(a)$ $O^{2-}$ | $(i)$ $18$ |
| $(b)$ $Li^{2+}$ | (ii) $2$ |
| $(c)$ $He$ | (iii) $10$ |
| $(d)$ $Ca^{2+}$ | (iv) $1$ |

Identify the isobars and isotopes from the following: $_6^{14}C, _6^{13}C, _7^{14}N, _6^{12}C$

Assertion : The sum of protons and neutrons is always different in isobars.
Reason : Isobars are atoms of different elements having same mass number but different atomic number.

The number of electrons in a neutral atom of an element is equal to its