Review: Elements

Elements  A pure substance made up of only one type of atom.  Every known element is listed on the periodic table.  Examples: sodium and oxygen

Physical Properties  Any feature of a substance, such as an element, that can be OBSERVED or MEASURED.  Examples:  Colour  State (solid, liquid or gas)  Lustre (shiny or dull)  Boiling Point

Physical Properties of Sodium  Colour?  Silver  State?  Solid  Lustre?  Shiny  Boiling Point?  883°C

Chemical Properties  Describe how substances, such as elements, will BEHAVE when in contact with another substance.  Examples:  Reactivity with oxygen  Combustibility  Reactivity with water

Chemical Properties of Sodium  Reactivity with water?  Reactivity with oxygen?  Sodium turns white  Combustibility?  Catches on fire very easily reactions of alkali metals

Atoms  The smallest unit of an element  Made up of sub-atomic particles. Sub-atomic Particle Electrical Charge SymbolLocation Proton+ p+p+p+p+Nucleus Electron- e-e-e-e- Around the nucleus NeutronNeutral (no charge) n0n0n0n0Nucleus

Look at the Periodic Table!!!  Protons = Atomic Number  Electrons = Atomic Number  Neutrons = Atomic Mass – Atomic Number ATOMIC NUMBER ATOMIC MASS

Atoms of Sodium  Protons = Atomic Number  Electrons = Atomic Number  Neutrons = Atomic Mass – Atomic Number ATOMIC NUMBER ATOMIC MASS Protons = 11 Electrons = 11 Neutrons = 23 – 11 = 12

Bohr – Rutherford Diagrams  Diagram of an atom  Remember:  Nucleus: Protons and Neutrons  Around the nucleus in shells: Electrons  1 st shell: 2 electrons max  2 nd shell: 8 electrons max  3 rd shell: 8 electrons max

B-R of Sodium P = 11 E = 11 N = 23 – 11 = 12 P = 11 N = 12 VALENCE SHELL VALENCE ELECTRONS = 1