Atoms

Atoms

1. From the Greek word "atomos", meaning indivisible

2. Made up of 3 sub-atomic particles

   • Protons - Positively Charged sub-atomic particles. Contained in the nucleus.
   • Electrons - Negatively charged subatomic partivles. Orbit the nucleus in 'shells'
     • The number of protons and electrons are usually the same. This results in the elements having an overall neutral charge (not positive or negative)
       • IONS - Elements with a positive (cation) or negative (anion) charge as the result of gaining or losing electrons.
         • Ionic Bond - Metal + Non-Metal + ide
   • Neutrons - Have no charge (not positive or negative). Contained in nucleus with protons. Act as a 'glue' to hold together the protons.

3. The building block for all matter.

   • Elements - a pure substance of one type of atom.
     • The periodic table - is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties
       • Atomic Number - Smaller number shown of an element in a periodic table. The number of protons for that element.
       • Atomic Mass - The larger number shown. This is the sum of the protons and neutrons (protons + neutrons)
         • Isotopes - Atoms having the same number of protons but different number of neutrons.
       • Groups - the columns in a periodic table. The group number tells you how many electrons there are in the valence shell.
   • Compounds - Substances made of two or more separate elements that are chemically joined. E.g. H20
   • Mixtures - Substances made of 2 or more separate elements that are not chemically joined E.g. Orange juice, oil and water.

4. Chemical Changes

   • Chemical changes occur when a substance combines with another to form a new substance
   • Formed through chemical reactions
     • Chemical Reactions: Reactant + Reactant = Product
       • Reactant - An element or compound that react with another to form a product
       • Product - Formed by the combination of reactants during a chemical reaction
         • Precipitate - is the creation of a solid from a solution.
       • Solvent - a liquid capable of dissolving another substance
         • Solute - a substance that is dissolved in a liquid (the solvent)
       • 6 Types of Chemical Reaction
         • 1. Neutralisation Reactions - Between acids and bases
         • 2. Synthesis (or Combination) - the combination of 2 or more substances to form a compound
         • 3. Decomposition - a compound breaks down into 2 or more simpler substances
         • 4. Single Replacement - a single element reacts with an ionic compound and switches places with one of the elements in the compound
         • 5. Double Replacement - cation of one compound combines with anion of the other
         • 6. Combustion Reaction - Hydrocarbon reacts with oxygen to produce carbon dioxide and water

5. Physical Changes

   • A physical change is any change NOT involving a change in the substance's chemical identity

6. Bohr Diagram

   • A simplified visual representation of an atom
   • Can be used to show the number of valence electrons in the valence shell (outer shell)

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