Neutrons, with protons and electrons, make up an atom. Neutrons and protons are found in the nucleus of an atom. Unlike protons, which have a positive charge, or electrons, which have a negative charge, neutrons have zero charge. Neutrons bind with protons with the residual strong force.
Neutrons were predicted by Ernest Rutherford, and discovered by James Chadwick, in 1932. Atoms were fired at a thin pane of beryllium. Particles emerged which had no charge, and he called these 'neutrons'.
Like all hadrons, neutrons are made of quarks. A neutron is made of two down quarks and one up quark. 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.
Isotopes[change | change source]
Neutrons can be found in almost all atoms together with protons and electrons. Hydrogen-1 is the only exception. Atoms with the same number of protons but a different number of neutrons are called isotopes of the same element.
The number of neutrons in an atom does not affect its chemical properties. However it affects its half-life, a measure of its stability. An unstable isotope has a short half-life, in which half of it decays to lighter elements. By contrast, a stable isotope has a long half-life, much longer than that of an unstable isotope. The stability of an isotope is related to radioactivity: an unstable isotope can be highly radioactive.
Atomic reactions[change | change source]
References[change | change source]
- Woolley, Steve (2011). Edexcel IGCSE Physics Revision Guide. Pearson Education. p. 20-21. .
- Cox, Brian; Cohen, Andrew (2011). Wonders of the Universe. HarperCollins. p. 79, 108. .
- Ryan, Lawrie (2001). Chemistry for you: revised National Curriculum edition for GCSE (Second ed.). Nelson Thornes. p. 29. .
- "Discovery of Neutrons". Helmholtz Zentrum Berlin. 2008-08-23. http://www.helmholtz-berlin.de/angebote/arbeiten-lernen/info/neutronen/entdeckung_en.html#c22033. Retrieved 2011-04-14.
- "The Nobel Prize in Physics 1935: James Chadwick". Nobelprize.org. http://nobelprize.org/nobel_prizes/physics/laureates/1935/. Retrieved 2011-04-15.
- "Neutron (subatomic particle)". Encyclopædia Britannica Online. Encyclopædia Britannica. Retrieved on 14 April 2011.
Other pages[change | change source]