Which of the following is not isoelectronic?

Atomic weights of carbon,nitrogen and oxygen are $12, 14$ and $16$ respectively. An atom of atomic weight $14$ and nuclear charge $+6$ is an isotope of

An isotone of $_{32}Ge^{76}$ is:
$(i) \, _{32}Ge^{77}$
$(ii) \, _{33}As^{77}$
$(iii) \, _{34}Se^{77}$
$(iv) \, _{34}Se^{78}$

The atomic weight of an element is $39$. The number of neutrons in its nucleus is one more than the number of protons. The number of protons,neutrons,and electrons respectively in its atom would be

The mass numbers of two elements $X$ and $Z$ are $52$ and $75$ respectively. $X$ contains $16.6 \%$ more neutrons compared to protons. $Z$ contains $27.3 \%$ more neutrons compared to protons. $X$ and $Z$ are respectively

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