ATOMS Atoms are the basic unit of matter

ATOMS • Atoms are the basic unit of matter. • Atoms are made up of neutrons, protons and electrons. • Neutrons are found in the nucleus and have no charge. • Protons are found in the nucleus and have a positive charge. • Electrons circle the nucleus and have a negative charge.

Energy Levels • Electrons circle the nucleus in energy levels. The first level holds up to 2 electrons, the second level holds up to 8 and the third holds up to 8. • Electrons fill the first level, then the second and then the third. • The first level is closest to the nucleus.

Elements, Isotopes and Ions • An element is made up of all the same kind of atoms. • An atom’s properties are determined by the number of protons. Carbon always has 6 protons (remember this!). • The number of neutrons or electrons may vary. An atom that has a different number of neutrons than protons is called an isotope. An atom that has a different number of electrons than protons is called an ion.

More……. Isotope example: Carbon always has 6 protons, but it may have 8 neutrons. Carbon that has 6 protons and 6 neutrons is called carbon 12 (C 12). Carbon that has 8 neutrons is called carbon 14 (C 14). Isotopes can be used to treat cancer or date fossils among other things. Ions: An atom that has more electrons than protons has a negative charge. An atom that has fewer electrons than protons has a positive charge.