3Structure of the atom Protons +1 charge Neutrons +0 charge Electrons chargeProtons and Neutrons are found together in the nucleus of the atomElectrons are found in discrete ‘orbital's’ outside the nucleus
4Atomic Number = #protons Mass Number = #protons + #neutrons (for an individual atom)An Isotope of an element occurs by adding or subtracting neutrons from that atomAtomic Mass = is the mass average of the naturally occuring isotopes of that element
5If an atom has more protons than electrons it has a net positive charge. These atoms are called cationsIf an atom has more electrons than protons it has a net negative charge. These atoms are called anions
6How big are protons, neutrons, and electrons How big are protons, neutrons, and electrons? It turns out that protons and neutrons are much heavier than electrons. Protons and neutrons weigh 1.67 x grams. Electrons weigh 9.11 x grams. Or put another way, protons and neutrons are 1800 times more massive than electrons. Therefore, most of mass of an atom comes from protons and neutrons.
7Discovery of Atomic Structure It was discovered in 1911 that most of the atom is empty space. If an atom were the size of a football stadium, the nucleus would be the size of a marble in center field, with electrons orbiting on the edge of the stadium.How was this discovered?
10The Rutherford Experiment In this experiment helium nuclei (alpha particles) are beamed at a thin piece of gold foil. Since atoms are mostly empty space, most of the helium nuclei pass through the foil. Occasionally, a helium atom will hit a gold nuclei and deflect it at different angles where it is detected by a fluorescent screen.
11Columns on the periodic table are called groups. Groups of elements have similar chemical properties:
12Phases of Matter Liquid Gas Plasma Can you identify examples of each? SolidLiquidGasPlasmaCan you identify examples of each?Solid: Desk, Floor, TextbookLiquid: WaterGas: Air we BreathePlasma: Fluorescent Lights, Sun