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1. Atoms

   • The Nucleus
     • Contains protons and neutrons
       • Has a positive charge because of the protons
         • Whole mass concentrated in nucleus.
     • The Electrons
       • Whizz around the nucleus.
         • Negatively charged
           • No Mass
   • Number of protons = Number of Electrons
   • If electrons are added or removed, the atoms become charged = Ion
   • Atoms of the same element all have the same no. of protons. Atoms of different elements will have different numbers of protons.

2. Chemical Reactions

   • How to Balance Equations
     • 1: Find an element that doesn't balance and put in a number.
       • See where it gets you. Put in another number and see where that gets you.
         • 3. Carry on unbalancing elements until the whole equation is done.
   • State Symbols:
     • (s) - Solid
     • (l) - Liquid
     • (g) - Gas
     • (aq) - Aqueous : Dissolved in water / Soluble

3. Line Spectrums

   • Some elements produce flames with an indicative colour
     • Lithium: Red
     • Sodium: Yellow/Orange
     • Potassium: Lilac
   • Each element gives a characteristic line spectrum.
     • This is because energy is released as light.
       • Different elements emit different wavelengths of light, due to the electron arrangement.
         • Elements can be identified using line spectrums (Spectroscopy)
           • Caesium and Rubidium have been discovered by their line spectrum. Helium was discovered in the line spectrum of the Sun.

4. History of The Periodic Table

   • Döbereiner
     • Tried to organise elements into triads
       • Put the list of elements into groups based on their chemical properties.
         • Middle element of each triad had a relative atomic mass that was the average of the two.
   • Mendeleev
     • Arranged 50 known elements and left gaps.
       • Put elements in order of Atomic Mass (like Newlands)
         • Had to leave gaps in order to keep elements with similar properties in the same vertical groups.
           • Allowed to predict the properties of undiscovered elements.
             • When they were found and fitted the pattern, it helped confirm Mendeleev's ideas.
   • Newlands
     • If you arranged elements in Relative Atomic Mass (RAM), every eighth element had similar properties. Listed in rows of 7
       • The sets of eight were called Newland's Octaves.
         • The pattern broke down on the third row
           • He left no gaps, so he was ignored.
             • Work was criticised because:
               • 1. His groups contained elements that didn't have similar properties, eg. C and Ti
               • 2. He mixed up metals and non-metals, e.g. oxygen and iron.
               • He didn't leave any gaps for elements that hadn't been discovered yet.

5. Using the Periodic Table

   • Row = Period
     • As you move from left to right along a period, each element has one more proton and one more electron
       • Properties change across a period - called trends
   • Column = Group
     • Elements in Group 0 have full electrons and are inert (very unreactive)
       • Number of electrons in outer shell of an atom = Group Number
   • As you go from left to right, elements change from metals to non-metals
     • Atoms of elements with up to 3 electrons in their outer shell are metals
       • Atoms of elements with 5 or more electrons in their outer shells are non-metals.
         • Elements with full outer shells are the inert gases.
       • If you know the properties of one element, you can predict the properties of that other element in a group.

6. Electrons

   • Electrons are arranged in shells
     • The lowest energy levels are always filled first.
       • 1st Shell Holds 2
         • 2nd Shell holds 8
           • 3rd+ Shells hold 8
     • Atoms do not want shells that are not full, this makes them react.
     • An electron arrangement determines its chemical properties.

7. Ions

   • Made when Atoms gain/lose electrons
     • When atoms gain/lose electrons, they're trying to get a full outer shell.
       • All elements in Group 1 (e.g. Na, K) have just one electron in their outer shell.
         • They want to lose that shell.
           • When Group 1 elements lose an electron, they form positive ions (positive charge)
             • Ionic Compounds
               • Compounds of a G1 element or a G7 element (e.g. NaCl) are solids with HIGH melting points.
                 • These compounds are ionic compounds because they contain charged ions that are arranged in a regular pattern.
                   • This is called a CRYSTAL LATTICE or a GIANT LATTICE.
               • Properties
                 • Ionic Compounds are soluble in water and conduct electricity when melted.
                   • When an ionic crystal melts/dissolved in water, the ions are free to move.
                     • An ionic compound conducts electricity when molten or in solution but NOT WHEN SOLID. This is because the ions must move to the electrodes to complete the circuit.,
         • All elements in Group 7 (e.g. Chlorine, Bromine) have outer shells that are almost full.
           • They want to gain one extra electron to fill the shell up.
             • When Group 7 elements gain an electron, they form negative ions (negative charge)

8. Group 1 - The Alkali Metals

   • G1 elements are METALS and have one electron in the outer shell of their atoms
     • G1 elements are soft metals that can be cut with a knife. The freshly cut surface is shiny but tarnishes quickly in most air as it reacts with oxygen.
       • The physical properties of Group 1 , e.g. melting point, boiling point and density SHOW TRENDS DOWN THE GROUP.
         • ALL FORM +1 IONS by losing an electron
           • The outer electron is easier to lose if the atom is bigger, because the electron is further away from the nucleus. So reactivity increases down G1 as atoms get bigger
         • As you go down G1, the ALKALI METALS:
           • MORE REACTIVE
           • HIGHER DENSITY
           • LOWER MELTING POINT
           • LOWER BOILING POINT
   • Metal + Water --> Metal Hydroxide + Water
     • Sodium + Chlorine --> Sodium Chloride

9. Group 7 -

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