6th period  All matter is made of atoms and can’t be created, divided or destroyed  Atomic theory – Democritus first came up with idea of atom. Dalton, Thomson, Rutherford, Bohr developed atomic theory building on the predecessors work.  Atoms made of protons, neutrons and electrons  Electrons –, no mass, negative charge  Neutrons – 1 amu, nucleus, around the nucleus in the electron cloud no charge (neutral)  Protons – 1 amu, positively charged, nucleus,  Nucleus is positive  mass of atom is in nucleus  Atomic mass = protons+neutrons  Isotopes – different number of neutrons  Atoms – smallest particle that an element can be divided into and still be that element. 4th Period  Atomic Theory – Dalton, Thomson, Rutherford,  Neils Bohr is current  Nucleus – in center of the atom. Made of protons and neutrons. Surrounded by electron cloud  Electon – negative charge. No mass, around nucleus in electron cloud, can’t determine their speed and location at the time  Proton – positive charge, nucleus, 1 amu  Neutrons – neutral charge, nucleus, 1amu  Mass = protons + neutrons  Atomic number – total number of protons  Nucleus – mass of atom is here, positive charge 3rd Period  Atomic Theory Development: Dalton, Thomson, Rutherford, Bohr  Protons – in nucleus, positive, 1amu  Neutrons – nucleus, no electric charge (neurtral), 1 amu,  Electrons – outside nucleus in the electron cloud, negative, No mass 2nd Period:  Thompson – atoms made of smaller particles called electrons  Atomic theory: Dalton, Rutherford Bohr  Atom – smallest particle into which an element can be divided and still be that element  Protons – positive, in nucleus, mass 1 amu  Neutrons – no electric charge (neutral), nucleus, 1 amu  Mass of atom is all in nucleus  Electrons – negative charge, move around nucleus in the electron cloud.  Finding Atomic Mass: Add protons + neutrons 1st period  Model changed over the years – Dalton, Thompson, Rutherford, Bohr  Protons – positive, in nucleus, 1AMU  Neutrons – no charge (neutral), in nucleus, 1AMU  Electrons – negative, around nucleus (electron cloud), no mass  Finding Atomic Mass: Add protons + neutrons