1911

1. - - Nucleus + - 1911 Positively charge particle Electron Atom, Ion, and Molecule Negatively charge particle -

2. + + - - Proton Positively charge particle 1932 + Mesons 1947 Neutron Uncharge particle

3. - + + - Gluon 1968 Quark Up, Charm, Down, Top, Strange, Bottom

4. Atoms are made out of three basic particles : • Protons – carry a positive charge • (Ernest Rutherforddiscovered the proton in 1911) • Neutrons – carry no charge • (James Chadwickcontributed in the discovery of the neutron in 1932) • Electrons – carry a negative charge and circle the nucleus • (J. J Thomson discovered the electron in 1897 ) • Protons and neutrons are made up of smaller particles called quarks. • Quarks are held to each other by particles, scientists called it gluons SUMMARY

5. Mass of 1 proton = mass of 1836 electrons • Neutrons and protons have almost the same mass • Atoms always have as many electrons as protons • Atoms usually have about as many neutrons as protons e.g. Hydrogen (1 proton, 1 electron, 0 neutron) ; Helium (2 proton, 2 electron,2 neutron) ; Carbon ( 6 proton, 6 electron, 6 neutron). • Add a proton makes a new kind of atom • Adding a neutron makes an isotope (Greek isos = equal, tópos = site, place) of that atom,a heavier version of that atom. Isotope are any of the different types of atoms (Nuclides) of the same chemical element each having different atomic mass (mass number) THE FACTS