What is 1s 2s 2p 3s 3p ?

The notation "1s 2s 2p 3s 3p" represents the electron configuration of an atom. It describes the distribution of electrons among the atomic orbitals of the atom.

In this notation, the number represents the principal energy level (or shell) of the atom, and the letter denotes the type of atomic orbital. The letter "s" represents a spherical-shaped orbital, while the letter "p" represents a dumbbell-shaped orbital.

The numbers that precede the letters indicate the number of electrons occupying each orbital. For example:

1s: This indicates that the first energy level (n = 1) has one electron in the s orbital.
2s: This represents the second energy level (n = 2) and indicates that it has two electrons in the s orbital.
2p: This denotes the second energy level (n = 2) and indicates that it has six electrons distributed among the three p orbitals.
3s: This represents the third energy level (n = 3) and indicates that it has two electrons in the s orbital.
3p: This denotes the third energy level (n = 3) and indicates that it has six electrons distributed among the three p orbitals.
Overall, the electron configuration "1s 2s 2p 3s 3p" suggests that the atom has a total of 17 electrons.