Chemistry

There are 2 energy sublevels in the second principal.

Phosphorus has an electron configuration of 1s2 2s2 2p6 3s2 3p3. Another way to write that is [Ne] 3s2 3p3. The [Ne] represents the fact that the beginning of phosphorus' electron configuration is the same as Neon's.

the period number tells which is the highest energy level occupied by the electrons

The energy required to remove an electron from an atom

electrons that are closet to the nucleus

A full octet makes the noble gases nonreactive.

A covalent bond in which the electrons are shared equally

A bond in which electrons are unevenly shared between atoms

Halogens, specially fluorine

The lone pair repels the electrons of the adjacent bonds more so than does a bonding pair of electrons, so thus alters the molecular geometry of the molecule.

For example this is a salt.