What is Ar 5s2 4d10 5p5?

The notation Ar 5s2 4d10 5p5 represents the electron configuration of the element arsenic (As), which has an atomic number of 33. This notation indicates that arsenic has 33 electrons distributed among its electron shells. The "Ar" in the notation represents the electron configuration of the noble gas argon, whose electron configuration is [Ne] 3s2 3p6, and serves as a shorthand way to denote the core electrons of the atom. The 5s2 4d10 5p5 portion specifies the distribution of the valence electrons in the outermost energy levels of the arsenic atom.