During beta decay of a nucleus, how does the neutrons to proton ration change?

Explanation

Let us consider `beta`-decay of `._83Bi^(210)`
`._83Bi^(210) to ._84Po^(210)+ ._-1e^0`
Neutron to proton ratio before `beta`-decay
`=(210-83)/83=127/83`, and
Neutron to proton ratio after `beta`-decay
`=(210-84)/84=126/84`.
which is less than `(127)/(83)`.
Hence, the neutron to proton ratio decrease in `beta`-decay.