Sinonimi: cell nucleus
ETYM Latin, a kernel, dim. from nux, nucis, nut. Related to Newel post.
In biology, the central, membrane-enclosed part of a eukaryotic cell, containing the chromosomes.
1. The positively charged dense center of an atom.
2. A part of the cell containing DNA and RNA and responsible for growth and reproduction; SYN. cell nucleus.
3. (Astronomy) The center of the head of a comet; consists of small solid particles of ice and frozen gas that vaporizes on approaching the sun to form the coma and tail.
The nucleus of an atom is the central core that comprises almost all the weight of the atom. All atomic nuclei (except H-1, which has a single proton) contain both protons and neutrons.
In physics, the positively charged central part of an atom, which constitutes almost all its mass. Except for hydrogen nuclei, which have only protons, nuclei are composed of both protons and neutrons. Surrounding the nuclei are electrons, of equal and opposite charge to that of the protons, thus giving the atom a neutral charge.
The nucleus was discovered by New Zealand physicist Ernest Rutherford in 1911 as a result of experiments in passing alpha particles through very thin gold foil.
A few of the particles were deflected back, and Rutherford deduced that the deflection was due to the positively charged alpha particles being repelled by approaching a small but dense positively charged nucleus.