This site provides an introduction to the standard model of particle physics, the theory which is currently most widely accepted to describe the structure of matter. All of the elementary particles of matter and the fundamental forces are characterized and classified. The site also provides information about the testing of the standard model.
6-8: 4D/M1a. All matter is made up of atoms, which are far too small to see directly through a microscope.
9-12: 4D/H1. Atoms are made of a positively charged nucleus surrounded by negatively charged electrons. The nucleus is a tiny fraction of the volume of an atom but makes up almost all of its mass. The nucleus is composed of protons and neutrons which have roughly the same mass but differ in that protons are positively charged while neutrons have no electric charge.
9-12: 4D/H2. The number of protons in the nucleus determines what an atom's electron configuration can be and so defines the element. An atom's electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. Atoms form bonds to other atoms by transferring or sharing electrons.
9-12: 4D/H5. Scientists continue to investigate atoms and have discovered even smaller constituents of which neutrons and protons are made.
%0 Electronic Source %D December 11, 2008 %T The Standard Model of Particle Physics %I BBC %V 2015 %N 26 February 2015 %8 December 11, 2008 %9 text/html %U http://www.h2g2.com/approved_entry/A666173
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