Neutron

Neutrons, with protons and electrons, make up an atom. Neutrons and protons are found in the nucleus of an atom.^[1][2][3] Unlike protons, which have a positive charge, or electrons, which have a negative charge, neutrons have zero charge^[1][4] which means they are neutral particles. Neutrons bind with protons with the residual strong force.

Neutrons were predicted by Ernest Rutherford,^[5] and discovered by James Chadwick,^[6][7] in 1932.^[6] Atoms were fired at a thin pane of beryllium. Particles emerged which had no charge, and he called these 'neutrons'. They were later added to the modern image of the atom.

Neutrons have a mass of 1.675 × 10^-24g,^[8] which is a little heavier than the proton.^[8] Neutrons are 1839 times heavier than electrons.^[8]

Like all hadrons, neutrons are made of quarks. A neutron is made of two down quarks and one up quark.^[2][3] One up quark has a charge of +2/3, and the two down quarks each have a charge of -1/3. The fact that these charges cancel out is why neutrons have a neutral (0) charge. Quarks are held together by gluons.

1. ↑ ^{1.0 1.1} Woolley, Steve (2011). Edexcel IGCSE Physics Revision Guide. Pearson Education. p. 20-21. ISBN 9780435046736.
2. ↑ ^{2.0 2.1} Cox, Brian; Cohen, Andrew (2011). Wonders of the Universe. HarperCollins. p. 79, 108. ISBN 9780007395828.
3. ↑ ^{3.0 3.1} Nave, R. (2007-01-15). "Protons and neutrons". hyperphysics.phy-astr.gsu.edu. Retrieved 2011-07-15.
4. ↑ Ryan, Lawrie (2001). Chemistry for you: revised National Curriculum edition for GCSE (Second ed.). Nelson Thornes. p. 29. ISBN 9780748762347.
5. ↑ "Ernest Rutherford". chemed.chem.purdue.edu.
6. ↑ ^{6.0 6.1} "Discovery of Neutrons". Helmholtz Zentrum Berlin. 2008-08-23. Archived from the original on 2010-11-13. Retrieved 2011-04-14.
7. ↑ "The Nobel Prize in Physics 1935: James Chadwick". Nobelprize.org. Retrieved 2011-04-15.
8. ↑ ^{8.0 8.1 8.2} "Neutron (subatomic particle)". Encyclopædia Britannica Online. Encyclopædia Britannica. Retrieved 2011-04-14.