How many sets of quantum numbers must be used to describe the electrons in a neutral beryllium atom?

You must use four sets of quantum numbers.

Step-by-step explanation:

A neutral Be atom has four electrons, and each electron has its own unique set of the four quantum numbers n, l, mₗ and mₛ.

Here is the set of quantum numbers for each electron.

Electron   n     l    mₗ   mₛ

     1           1     0     0    +½

    2           1     0     0    -½

    3           2    0     0    +½

    4           2    0     0    -½