# Can the electron configuration of Te be written that way?

Normally, the electron configuration of Te is known as:

\begin{aligned} {[Kr]} 5s^2 \ce{4d^10} 5p^4 \end{aligned}

Then, one day I was asked in a exam if this can be written also as:

\begin{aligned} {[Kr]} 5s^2 \ce{4d^10} 5p^3 6s^1\end{aligned}

I answered that it couldn't. But my answer turned out to be wrong.

If this is correct, why is it allowed to be written like this? And what general case can I learn when being asked such tricky questions?

Similar behavior is what allows carbon to form 4 bonds. The $\ce{s^1p^3}$ configuration is more stable than the $\ce{s^2p^2}$.