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

An element has an atomic weight of $40$ and its electronic configuration is $1s^2 2s^2 2p^6 3s^2 3p^6$. What are its atomic number and the number of neutrons?

In the two elements, ${ }_{Z_1} A^{M_1}$ and ${ }_{Z_2} B^{M_2}$, the following relations are true. $M_1 \neq M_2$ and $Z_1 \neq Z_2$ but $M_1-Z_1=M_2-Z_2$. These elements are ($M$ is atomic weight, $Z$ is atomic number)

An ordinary oxygen sample contains:

Number of neutrons in ${}^{12}C$ is

The number of electrons in $[_{19}^{40}K]^{-1}$ is