Helium (He), neon (Ne), and argon (Ar), as group 18 elements, have outer electron shells that are full or satisfy the octet rule. This makes them highly stable as single atoms. Because of their non-reactivity, they are called the inert gases or noble gases.

four

Shell number one can only hold 2 electrons, shell two can hold 8, and for the first eighteen elements shell three can hold a maximum of eight electrons. That means there are 6 electrons in a carbon atom.

The Group 7 elements – fluorine (F), chlorine (Cl), bromine (Br), iodine (I) and astatine (At) – have seven electrons in the outer shell.

This gives the following order for filling the orbitals: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, (8s, 5g, 6f, 7d, 8p, and 9s)

An electron shell is the outside part of an atom around the atomic nucleus. It is a group of atomic orbitals with the same value of the principal quantum number n. Electron shells have one or more electron subshells, or sublevels.

There can be two electrons in one orbital maximum. The s sublevel has just one orbital, so can contain 2 electrons max. The p sublevel has 3 orbitals, so can contain 6 electrons max.

Types of orbit

• Geostationary orbit (GEO)
• Low Earth orbit (LEO)
• Medium Earth orbit (MEO)
• Polar orbit and Sun-synchronous orbit (SSO)
• Transfer orbits and geostationary transfer orbit (GTO)
• Lagrange points (L-points)

18 electrons

Eighteen electrons