Helium is the second simplest atom. It consists of a nucleus containing 2 protons and 2 neutrons. Around the nucleus orbits 2 electrons.

The nucleus of a hydrogen atom consists of a single proton. Around this proton orbits a single electron.

Hubble images taken in October 2013 and March 2014 show two jets of dust coming from the comet's core, or nucleus.

Helium is the second simplest atom. It consists of a nucleus containing two protons and two neutrons. Around the nucleus orbits two electrons.

If the comet nucleus is pulled into an orbit which carries it close to the Sun, the solar heat will cause the outer layers of the icy nucleus to evaporate.

The protons and neutrons cluster together in the center of the atom in what is called the nucleus. The electrons orbit around the nucleus.

The atom's nucleus is surrounded by an electron cloud.

The nucleus and optional coda of a syllable are called the rime.

You two are the nucleus of the team.

A great deal of energy is locked up in the nucleus.