Fundamental Ideas in Chemistry

Atoms
1. Atoms are the smallest part of an element
  1. Elements are made up of only one type of atom
2. Elements are represented by 1, 2 or 3 letters e.g. oxygen-O, sodium-Na
3. Atomic Structure
  1. An atom has a small central nucleus containing sub-atomic particles called protons and neutrons
    1. The nucleus is surrounded by smaller sub-atomic particles called electrons
      1. Each proton and electron has an electrical charge
        Protons have a positive charge (+1) and electrons have a negative charge (-1)
        Neutrons do not have any electrical charge; they are neutral
        The number of protons in an atom is equal to the number of electrons, therefore atoms have no electrical charge
  2. The atomic number (shown at the bottom) of an element is the number of protons (and electrons) it has in one atom
    1. The mass number (shown at the top) of an element is the number of neutrons and protons a single atom has
4. Electronic structure
  1. Electrons in an atom occupy energy levels (or shells)
    1. The first shell fills up first followed by the next
    2. The first energy level can only hold 2 electrons, the second shell can only hold 8 and the third can only hold 8
    3. The number of shells and the number of electrons in the outermost shell is relative to the group and period an element is placed in
      1. E.g an element with 2 shells will be in period 2 and an element with 3 electrons in the outer shell will be in group 2
The Periodic Table
1. There are around 100 elements and they are all listed and arranged specifically in the periodic table
2. The horizontal rows are called periods and the vertical columns are called groups
  1. Elements in the same group have similar properties
3. Elements are split into two types; metals (found on the left of the periodic table) and non-metals (on the right)
  1. Most elements are metals
4. Elements found in the 1st group are all very reactive metals
  1. They are called Alkali metals because they form alkaline compounds
  2. Lithium, sodium and potassium react vigorously with water so all group 1 metals must be stored in oil in order to stop them reacting with the oxygen and water vapour in the air
  3. Lithium, sodium and potassium are easily cut with a blade. The freshly cut surfaces are silvery and shiny, but quickly turn dull as the metal reacts with oxygen in the air
5. Elements found in group 7 are all very reactive non-metals
6. Elements found in group 8 are very un-reactive and are called noble gases
Chemical reactions
1. New substances are formed when chemicals react
  1. When elements react, their elements join with other atoms to make compounds
  2. Compounds usually have different properties from the elements they are formed from
2. Ionic bonds
  1. Compounds formed from a metal and a non metal consists of ions
    1. Ions are charged particles that form when atoms gain or lose electrons
      1. Metals lose atoms to become positively charged ions
        Ionic bonding is the force of attraction between negatively and positively charged ions
      2. Non metals gain electrons to become negatively charged ions
3. Covalent bonds
  1. Covalent bonding occurs when two non-metals share electrons between each other
4. Chemical Formulas
  1. The chemical formula of an atom shows us which elements are in a compound and how many atoms of each element there are
5. The Conservation of Mass
  1. No atom can be lost or made during a chemical reaction
    1. Therefore the total mass of atoms in the chemicals before a chemical equation is always the same as the total mass of atoms in the products of a chemical reaction

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	Created by seth.bragg over 11 years ago