Conversations with the Earth Tom Burbine

Chemistry The science of matter and the changes it undergoes.

Atoms Atoms are made up of 3 types of particles Protons – positive charge (+1) Electrons – negative charge (-1) Neutrons – neutral charge (no charge) Protons and Neutrons are found in the nucleus

Elements Different elements have different numbers of protons The properties of an atom are a function of the electrical charge of its nucleus

Definitions Atomic Number – Number of protons Atomic Mass – Number of protons and neutrons U 235 – atomic mass 92- atomic number Isotopes – Same number of protons but different numbers of neutrons

Periodic Table A chart in which all known elements are listed in order of atomic number

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Period – Horizontal row Across any period, the properties of elements change Group – Vertical column Down any group, the properties of elements are very similar

Radioactivity Radioactivity – decay of an atomic nucleus All elements with an atomic number greater than 82 (lead) are radioactive

Bohr’s Planetary Model Electrons orbit the nucleus in specific energy levels Level n=1 is closest to nucleus Level n=2 is second closest

Shell Model Electrons behave as they are arranged in a series of concentric shells around the nucleus Innermost shell can contain 2 electrons The second and third shells can contain 8 electrons each The fourth and fifth shells can contain 18 electrons each

Valence electrons are the electrons in the outermost shell These electrons participate in chemical bonding

Ion Ion – an electrically charged particle created when an atom either loses or gains one or more electrons

Ionic Bond Ionic bond – chemical bond in which an attractive electric force holds an opposite charge together

Covalent Bond Covalent bond – a chemical bond in which atoms are held by their mutual attraction for two or more electrons share Molecules are held together by covalent chemical bonds

Metallic Bonds Atoms "share" electrons that float about in a general electron cloud

Charges need to balance Na ions carry a +1 charge Cl ions carry a -1 charge Na + + Cl - → NaCl (Sodium chloride)

HCl – Hydrogen Chloride Li 2 O – Lithium Oxide CO – Carbon Monoxide CO 2 – Carbon Dioxide

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Any Questions?