Question

Polonium- 207 may undergo three kinds of undergo radioactive decay: ${\mathbf{\beta }}^{\mathbf{+}}\mathbf{,}\mathbf{\alpha }$ and electron capture but it does not ${\mathbf{\beta }}^{\mathbf{-}}$decay. Given its position relative to the curve of stability, explain why this is not unexpected.

Short answer

If Polonium-$207$undergo ${\mathrm{\beta }}^{-}$ decay, it would gain a charge, which means it would become Astatine-$207$.

Since the curve of the stability shows that neutron should increase as proton increase, the decay proposed that loses a neutron loses a neutron but gain a proton would not be stable.

Step-by-step solution

Given data 

The given element is Polonium- $207$.

Concept of  β decay

In Nuclear Physics, Beta decay ( $\mathbf{\beta }$ decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide.

Explain how Polonium-207 does not undergo β-  decay

If Polonium-$207$underwent ${\mathrm{\beta }}^{-}$decay, it would gain a charge, which means it would become Astatine- 207.

Since the curve of the stability shows that neutron should increase as proton increase, the decay proposed that loses a neutron loses a neutron but gain a proton would not be stable.