Chemistry- January Exams 2018

?
  • Created by: 14gpowell
  • Created on: 28-12-17 14:53
View mindmap
  • Atomic Structure and the Periodic Table
    • Structure of atoms
      • Central nucleus containing protons and neutrons. It is surrounded by electrons in every levels sometimes known as shells
      • Atoms have no electric charge because they contain the same number of protons and electrons.
        • Atomic Number= number of protons
          • Mass number= number of protons+ number of electrons
      • proton- relative mass=1, relative charge=+1
        • neutron- relative mass=1, relative charge=0
          • electron- relative mass=1/1842,relative charge=-1
            • number of electrons= atomic number
          • number of neutrons= mass number- atomic number
        • number of protons= atomic number
          • It is the number of protons that determines what type of atom it is. Atoms of different elements have different numbers of protons.
      • neutron- relative mass=1, relative charge=0
        • electron- relative mass=1/1842,relative charge=-1
          • number of electrons= atomic number
        • number of neutrons= mass number- atomic number
      • Isotopes are atoms with the same no. of protons but a different number of neutrons. This therefore means that they are atoms of the same element with the same atomic number but a different mass number
      • The electrons in an atom orbit the nucleus, they are in a series of orbits known as shells. Each shell can only hold a fixed amount of electrons and therefore when they are full any remaining electrons enter the next shell
        • The first shell can hold 2 electrons
        • The second shell can hold  8 electrons
        • The third shell can hold 8 electrons
      • The group number of an element indicates the number of electrons in the outer shell
    • The Periodic Table
      • History of the Periodic Table
        • Greek philosophers thought that the world was made up of 4 elements: Earth, Air, Water and Fire
          • Antoine Lavoisie put the elements into groups
            • Johann Wolfgang Dobereiner discovered similar triads of elements
              • John Newlands discovered the law of octaves- every 8th element is the same as the 8th before it
                • Dimitri Mendeleev left gaps for elements he thought still had to be discovered and swapped order around to fit properties
                  • 1869
                • 1865
              • 1829
            • 1789
          • Aristotle etc.
        • The group number determines the number of electrons in the outer shell
        • Group 1 elements- 1 electron in outer shell. All metals. All react w/ oxygen to produce an oxide. All react with water to form an alkaline. All have a low density
          • Alkali Metals. They are all silvery grey solids which are soft and easily cut with a knife. They are shiny when freshly cut but quickly tarnish when they react with air.
          • The melting and boiling points increase as you go down the group
          • The elements at the bottom of the group have higher masses than those at the top.
          • The reactivity increases as you go down the group.
            • With non-metals- form ionic compounds and can lose their outer shell electron to form a 1+ion. The compounds formed are white, crystalline solids which dissolve in water to give a colourless solution.
              • With water- form a metal hydroxide(alkaline solution) and hydrogen gas
          • When the alkali metal react they loose an outer shell electron. On moving down the group it becomes easier to lose an electron as the outer shell is further from the nucleus (DISTANCE) and they is more filled shells of electrons between positive charge of ulcers and negative electrons (SHIELDING)
            • Force of attraction between the nucleus and electron decreases.
        • Group 7 elements all have 7 electrons in the outer shell.
          • The Halogens exist as molecules which are pairs of atoms
          • Non-metals that have coloured vapours
            • Fluorine is a poisonous yellow gas
            • Chlorine is a dense green gas
            • Bromine is a poisonous dense red-brown volatile liquid or an orange vapour
            • Iodine is a poisonous dark-grey crystalline solid or a purple vapour.
          • Reactivity decreases down the group as they react by gaining an electron
            • A more reactive halogen can displace a less reactive halogen
          • Melting and boiling point increases down the group
          • Relative atomic mass increases as you go down the group
        • All Group 0 elements (Noble gases) have 0 electrons in their outer shell and are all halogens. they are not flammable. At room temp they exist as colourless, monatomic gases
          • No very reactive (Stable arrangement of electrons in the outer shell)
          • As you go DOWN the group, the boiling point increases along with increasing atomic mass.(no. of electrons increases)
      • Elements are arranged in atomic number.
      • It is knowns as the periodic table as there is a periodic variation in properties
      • The Transition elements
        • Middle block of the periodic table. Good conductors of heat and electricity and very dense, strong and shiny
        • If you compare these to the group 1 elements, y ou find that they are less reactive and don't react vigorously with water and oxygen, they're much denser harder and stronger. They have much higher melting points.
        • They can form ions with different charges and these different ions usually form different coloured compounds.
          • The colours in gemstones are due to transition metals.
        • They make good catalysts

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Atoms resources »