4 Questions to ask...How did we find out that gold was gold and silver was something different?How did we find out what part of a particle makes a substance unique?How can models of the atom help explain matter?
5 Democritus (400 BCE)- Greek philosopher- All matter can be divided into smaller and smaller pieces- He called the last piece that “cannot be cut” an ATOM
6 Democritus’ Atomic Theory atoms are different sizesatoms are in constant motionatoms are separated by empty spaces
8 Aristotle (~340 BCE) Rejected the idea of the atom All matter is made up of 4 substancesEarth, Water, Fire and Air
9 - each atom of one material is the same - atoms cannot be divided John Dalton (1807)Billiard ball model- each atom of one material is the same- atoms cannot be divided
10 Dalton’s Atomic ModelAll mater is made up of tiny, indivisible particles called atomsall atoms of an element are identicalatoms of different elements are differentatoms are rearranged to form new substances in chemical reactions, but they are never created or destroyed
11 J.J. Thomson (1897)Discovered electrons- negatively charged particles“Plum Pudding” model- negative electrons embedded in a positive atom- electrons are evenly distributed
12 Ernest Rutherford (1909) Discovered the nucleus is very small contains most the masssurrounded by a cloud of negatively charged electronsmost of the atom is empty space
14 Niels Bohr (1913) Bohr refined Rutherford's model: - Electrons orbit the nucleus (like planets)- Electrons cannot be between orbits / they can jump between orbits- Each orbit can hold a maximum number of electrons
15 James Chadwick (1932) Student of E. Rutherford The nucleus contains 2 particlesPositive Protons (discovered by Rutherford in 1920)Neutral NEUTRONSA neutral atom contains the same number of protons and electrons
16 Type of Subatomic Particles ProtonNeutronElectronCharge+O-Locationin nucleusorbiting nucleusRelative Mass11/2000
17 The Bohr-Rutherford Model is what we will use (for the first 20 elements).
18 Have we met our Learning Goals? Can YOU explain how different atomic models evolved as a result of experimental evidence?Can YOU describe the characteristics of neutrons, protons and electrons (charge, location and relative mass)?
19 Group Task1. Create a TIMELINE of the history of the atom.OR2. Create a mini poster of the 1 you think is MOST important