C3

In the Early 1800s they could only go on atomic mass: Whereas now there are two obvious ways to categories elements: 1. Their physical and chemical properties 2. Their relative atomic mass

Newland's Law of Octaves:

In 1864 he noticed that every eight element had similar porperties, so he listed some of the known elements in rows of 7(Newland's octaves). However, not all the elements fitted the patern; titanium and iron do not have similar properties for example.                                                       Criticisms:                                                                                                                             -his groups contained elements with non-similar properties(titanium and carbon).                             -he mixed up metals and non-metals(oxygen and iron).                                                                -he didn't leave any gaps for undiscovered elements.

Mendeleev:

In 1869 Dimitri Mendeleev arranged elements in order of atomic mass but left gaps so that elements with similar properties were in columns. The gaps helped to predict properties of far undiscovered elements.

Lithium (Li), Sodium (Na), Potassium (K).....(Rb...Cs...Fr)

Low melting + boilings points that decrease as you go down group

Low density (Li, Na + K float on water)

More reactive as you go down group (Li < reactive than K). (Outer electron is further away so lost easily.)                  *((o))                   *((((o))))

One electron in outer shell = similar properties. 

React vigorously with water and oxygen (must be stored in oil).

Alkali Metal + Water ---> Metal Hydroxide and Hydrogen (Squeeky pop test!)

React with non-metals to form IONIC COMPOUNDS. Become +1 metal ions. Form white soluble solids (i.e Table Salt NaCl)

Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I)...(At)

Melting + Boling points increase as you go down group (fluorine gas, bromine liquid at room temp)

Coloured vapours.

Diatomic Molecules (exist as pairs of atoms)

Less reactive as you go down group (Outer shell is further away, so electrons are not as attracted by influence of nucleus) (F > reactive than l )
                                                            *----> ((o))                 (((((o))))) <- - *

Produce IONIC SALTS with metals (i.e Table Salt NaCl). Form Halide Ions (-1)

React with non-metals to form molecular compouns (i.e 2HCl). 
More reactive halogen will displace less reactive (i.e chlorine will displace bromine and iodine, but NOT fluorine)