Chemistry

a numbering system for the periodic table.

Or a trend that periodically shows up.

1s 2 2s 2 2p6 3s2 3p6 4s2

or

Ar 4s2 (Noble gas form)

In noble gas form, you go back to the noble gas (the last group on the periodic table) prior to the element you are writing the configuration for. The electron configuration is the same up until that point. Then you write down the difference.

In this example, the electron configuration for Argon (Ar) is 1s2 2s2 2p6 3s2 3p6. If you fill up the shells until 4s2, you get calcium. It's faster to abbreviate by saying "Ar 4s2"

Helium has the highest first ionization energy and francium has the lowest first ionization energy.

Barium(Ba)

magnesium (Mg)

question: which of the following elements is the smallest?

answer: chlorine (CI)

A chemical bond holds atoms together