Question

electrons orbit around the nucleus in circular path called
, or
.
the first shell is called
.
the second shell is called
.
the third shell is called
.
the fourth shell is called
.

Explanation:

Electrons orbit around the nucleus in circular paths called shells, energy levels, or orbits. The first shell is the K - shell, the second is the L - shell, the third is the M - shell, and the fourth is the N - shell. This is based on the Bohr model of the atom.

Answer:

shells, energy levels, orbits; K - shell; L - shell; M - shell; N - shell