PARTICLE RELATIVE MASS CHARGE
PROTON 1 +1
NEUTRON 1 0
ELECTRON 0.0005 -1
PHYSICAL STATE STATE SYMBOL
DISSOLVED IN WATER (aq)
ELEMENT COLOUR FLAME
LITHIUM (Li) RED
SODIUM (Na) YELLOW/ORANGE
POTASSIUM (K) LILAC
Different elements have different wavelengths and these wavelengths can be recorded as a line spectrum. They have different wavelengths due to their different electron arrangement. This means line spectrums can identify elements.
Elements that have been discovered by the line spectrum: CAESIUM, RUBIDIUM & HELIUM
HISTROY OF THE PERIODIC TABLE 1
1) Dobereiner - TRIADS (3s)
He tried arranging elements in order of relative atomic mass & the middle element of each triad had a relative atomic mass that was the average of the other two.
HISTORY OF THE PERIODIC TABLE 2
2) Newlands' Law of Octaves (8s)
He noticed that when you arranged the elements in order of realtive atomic mass, every eighth element had similar properties. Transition metals messed up his pattern. He was also criticised because he mixed up metals and non-metals & he didn't leave any gaps for elements that had not yet been discovered.
HISTORY OF THE PERIODIC TABLE 3
3) DMITRI MENDELEEV (present)
He put the elements in order of atomic mass and left gaps for new elements to be discovered. The gaps predicted the properties of undiscovered elements. To start with there was no evidence that the elements did fit together in that way but when new elements were discovered and fit in the gaps it was evidence in favour of the periodic table.
THE MODERN PERIODIC TABLE
- Elements with similar properties form columns
- The group number tells you how many electrons there are in the outer shell
- The rows are called periods, and each period represents a full shell of electrons
- If you know the properties of one element, you can predict the properties of the rest of the elements in the group
When atoms lose or gain electrons they form charged particled called ions.
Compounds formed between GROUP 1 and GROUP 7 elements are held together by IONIC BONDS
Ionic compounds form a regular or giant lattice. Each lattice forms a single crystal. When ionic compounds become molten or are dissolved in water than can conduct electricity because the ions are free to move. The fat that molten compounds made of metals and non-metals conduct electricity is evidence they're made up of ions.
IONS & FORMULAS (Easy)
Easy: When the ions in the compound have the same size charge
EXAMPLE: Find the formula for lithium fluoride.
Lithium ion is Li+ & Fluoride ion is F-
So the formula of lithium fluoride must be: LiF
IONS & FORMULAS (Harder)
EXAMPLE: Find the formula for calcium chloride.
Calcium ion is Ca2+ and Chloride ion is Cl-
To balance, you need 2 chloride ions to every 1 calcium ion
So the formula of calcium chloride is: CaCl2
GROUP 1 - THE ALKALI METALS
They are shiny when freshly cut but react with oxygen in the air
As you go DOWN Group 1, the alkali metals:
1) become MORE REACTIVE
2) have a HIGHER DENSITY
3) have a LOWER MELTING POINT
4)have a LOWER BOILING POINT
GROUP 1 - THE ALKALI METALS (Reactants)
GROUP 1 elements:
Reacting with COLD WATER produces HYDROGEN GAS (squaeky pop test)
2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g)
Reacting with CHLORINE produces SALTS
2Li(s) + Cl2(g) → 2LiCl(s)
GROUP 7 - THE HALOGENS
The halogens form diatomic molecules (pairs)
As you go DOWN Group 7, the halogens:
1) become LESS REACTIVE
2) have a HIGHER MELTING POINT
3: have a HIGHER BOILING POINT
ELEMENT COLOUR (AT R.T.) STATE (AT R.T.)
FLUORINE YELLOW GAS
CHLORINE GREEN GAS
BROMINE ORANGE LIQUID
IODINE GREY SOLID
The reactions become less vigorous as you go down the group
REACTIONS WITH ALKALI METALS
Halogens react with alkali metals to make SALTS called METAL HALIDES
REACTIONS WITH IRON
Halogens react with iron to form COLOURED SOLIDS called IRON HALIDES
A displacement reaction is where a more reactive element pushes out a less reactive element from a compound (this happens within the halogens for example, potassium chloride)
HIGHLY FLAMMABLE EXPLOSIVE
CHEMICAL SAFETY - ALKALI METALS
- Make sure there is a fire extinguisher - Group 1 elements are very reactive and can combust spontaneously. There can be a violent reaction if they come in to contact with water vapour in the air, so they're stored in oil to prevent this.
- Do not touch alkali metals with bare hands - sweat can cause a reaction that produces heat and a corrosive hydroxide.
- Keep every piece of apparatus completely dry
- Keep away from eyes and skin - alkaline solutions can be corrosive
CHEMICAL SAFETY - HALOGENS
- Chlorine and Iodine are both very toxic.
- Fluorine is too dangerous to have inside the lab.
- Contact with liquid bromine on the skin must be avoided - corrosive
- Must be used inside a fume cupboard as the halogens have poisonous vapours