C4

C4

1. Atoms

   • Number of protons = Number of electrons

2. Chemical Equations

   • (s) = Solid
   • (l) = Liquid
   • (g) = Gas
   • (aq) = Dissolved in water
   • When balancing equations, balance one atom at a time

3. Line Spectrums

   • Lithium, Li, - red flame
   • Sodium, Na, - yellow/orange flame
   • Potassium, K, - lilac flame
   • Spectroscopy
     • The practical technique used to produce line spectrums
     • 1. When heated, electrons in an atom release energy as light
     • 2. The wavelengths emitted can be recorded as a line spectrum
     • 3. Different elements have different wavelengths of light because each element has a different electron arrangement
     • 4. Each element has a different pattern of wavelengths, and a different line spectrum
     • 5. Line spectrums can be used to identify elements

4. History of The Periodic Table

   • Dobereiner
     • Organised elements into groups based on chemical properties, called triads
     • The middle element of each triad had a relative atomic mass that was the average of the other two
     • For example, Lithium, Sodium and Potassium
   • Newlands
     • Noticed that when you arranged the elements in the order of their RAM, every eighth element had similar properties, so he listed the known elements in rows of seven
     • Called these sets 'Newlands' Octaves'
     • Pattern broke down on third row, with transition metals like titanium and iron messing it up
     • Left no gaps for new elements, so work was ignored
     • Presented ideas of Chemical Society in 1865, but he was criticised because...
       • Groups didn't contain elements with similar properties
       • Mixed up metals and non-metals
       • Didn't leave gaps for elements that hadn't been discovered yet
   • Dmitri Mendeleev
     • Placed elements in order of RAM
     • Left gaps to keep elements with similar properties in the same vertical groups
     • Predicted properties of undiscovered elements that could fit in the gaps that he left

5. The Modern Periodic Table

   • Elements laid out in order of increasing proton number
   • Metals are found to the left and non-metals to the right
   • Elements with similar properties form columns
   • The vertical columns are called groups
   • The group number tells you how many electrons there are in the outer shell
   • The rows are called periods
   • From the periodic table, we can get the RAM, the proton number, the name and the symbol of the element

6. Electron Shells

   • 1st shell: 2, 2nd shell: 8, 3rd shell: 8 etc
   • Electrons prefer full outer shells

7. Ionic Bonding

   • When atoms lose or gain electrons they form charged particles called ions
   • When Group 1 elements lose an electron they form positive ions
   • When elements in Group 7 gain an electron. they form negative ions
   • Oppositely charged ions are strongly attracted to each other and this is called an ionic bond
   • For example, the sodium atom gives up its outer electron and becomes an Na+ ion and the chlorine atom picks up the spare electron and becomes a Cl- ion
   • Solid ionic compounds like sodium chloride are made up of a giant lattice of ions, and each lattice forms a single crystal. When ionic compounds become molten or are dissolved in water they can conduct electricity because the ions are able to move

8. Group 1 - The Alkali Metals

   • All have one electron in their outer shell
   • They are shiny when freshly cut, but quickly react with oxygen in moist air and tarnish
   • As you go down Group 1 the metals...
     • Become more reactive because the outer electron is easily lost because its further from the nucleus
     • Have a higher density because the atoms have more mass
     • Have a lower melting point
     • Have a lower boiling point
   • Reaction with cold water produces hydrogen gas, makes an alkaline solution and a hydroxide of the metal forms
   • Reaction with chlorine produces colourless crystalline salts

9. Group 7 - Halogens

   • Seven electrons in their outer shells, making them very reactive
   • As you go down Group 7, the halogens...
     • Become less reactive because the outer electrons are further from the nucleus and son additional electrons are attracted less strongly
     • Have a higher melting point
     • Have a higher boiling point
   • Form diatomic molecules which are pairs of atoms
   • Colours of Flames
     • Fluorine - a very reactive, poisonus YELLOW GAS at room temperature
     • Chlorine - a fairly reactive, poisonous dense GREEN GAS at room temperature
     • Bromine - a dense, poisonous, ORANGE VOLATILE LIQUID at room temperature and forms an ORANGE GAS
     • Iodine - a DARK GREY CRYSTALLINE SOLID at room temperature or a PURPLE VAPOUR
   • Reactions with alkali metals produce salts called metal halides
   • Reactions with iron produce coloured solids called iron halides
   • Displacement Reaction - where a more reactive element pushes out (displaces) a less reactive element from a compound

10. Laboratory Safety

    • Oxidising
    • Provides oxygen which allows materials to burn easily, like liquid oxygen
    • Explosive
    • Can explode - BANG, like some peroxides
    • Highly Flammable
    • Catches fire easily, like petrol
    • Corrosive
    • Attacks and destroys living tissue, including eyes and skin, like concentrated sulphuric acid
    • Toxic
    • Can cause death either by swallowing, breathing in, or absorption through the skin

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