C11

C11

C11.1
1. All substances are made up of atoms.
  1. Atoms can be found on their own, or in groups. When they're in groups, this is called a molecule.
  2. Atoms are made of protons, neutrons and electrons.
    1. Protons and neutrons are gathered in a cluster at the centre of the atom, whilst electrons orbit the atom in layers called shells.
      1. Electrons have a negative charge, where as protons have a positive charge and neutrons are neutral.
        An atom contains the same amount of protons and electrons, so it is not charged.
        The amount of protons in an atom is known as the atomic number.
        The mass number is the amount of protons and neutrons in the atom.
        To find out the number of neutrons, you must subtract the mass number and the atomic number.
2. A substance which contains only one type of atom is called an element.
  1. There are about 100 different elements, which can be found on the periodic table.
3. A mixture is a group of atoms which are not chemically bonded.
4. A compound is made up of more than one type of atom which have been chemically bonded.
5. An atom can have 2 electrons in its innermost shell, and up to 8 electrons in its other shells. In order to have electrons in outer shells, the inner shells must first be full.
C11.2
1. Rows of elements are called periods. Elements in the same period have the same amount of shells.
  1. Columns of elements are called groups. Elements in the same group have the same amount of electrons in their outer shell, and all have the same amount of reactivity.
    1. Elements in group 1 are called the alkaline metals, and elements in group 0 are called noble gases.
      1. The alkaline metals are the most reactive elements on the periodic table.
      2. The noble gases are almost inert..
C11.3
1. The periodic table can be divided into 3 groups:
  1. A metalloid is an element with some qualities of a metal, and some qualities of a non-metal.
    1. When you go down a group and to the left of a period, the elements get more and more reactive.
2. The alkali metals are so reactive that they are rarely found in nature, and have to be stored in oil to prevent them from reacting with the air.
  1. They are very soft and can be easily cut. They react with water to form alkaline compounds. They have a low density and low melting and boiling points.
    1. Alkali metals all have 1 electron in their outer shell.
      1. More reactive metals have more shells, because the further away an electron is from the nucleus of the atom, the easier it is for the electrons to be lost.
        alkali metal + water -> alkali metal hydroxide + hydrogen
        alkali metal + oxygen -> alkali metal oxide
3. The noble gases all form colourless gases at room temperature.
  1. Helium only has 2 electrons in it's outer shell, but all the other noble gases have 8.
C11.4
1. A chemical reaction is a change that takes place when one or more substances (called reactants) form one or more new substances (called products)
  1. Many chemical reactions are are irreversible changes. You can spot this by a colour change, a precipitate (solid) forming, an odour being produced, or energy being produced (which is shown by fizzing or burning.
  2. In a chemical reaction, electrons are either shared, lost or gained.
    1. An ion is a charged atom
      1. Ionic bonding takes place between a metal and a non metal. Electrons are taken, not shared. The metal atoms will lose electrons and become positively charged, and the non-metal atoms will gain electrons and become negatively charged. The ionic bond is the attraction between positive and negative ions.
    2. In covalent bonding, electrons are shared. It only occurs between non-metals. Each shared pair is a covalent bond.
    3. Metallic bonding occurs between metals. Metals lose electrons, which become delocalised. Because of these free-moving electrons, metals can conduct heat and electricity well. Metallic bonding is the attraction between positive metal ions and delocalised electrons.
  3. In a chemical reaction, the mass doesn't change. This is because no atoms are made or destroyed, the reaction just changes how atoms are bonded together.
C11.5
1. In an ionic compound, the non metal will be negatively charged and the metal will be positively charged.

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