Periodic Table

1964/65

Newlands noticed that every eighth element (atomic mass) had similar properties and so he arranged the known elements in rows of seven.

These sets of eight were known as Newlands' Octaves.

The pattern broke down on the third row due to transition metals such as titanium and iron.

His work was criticized as...

His groups contained elements that didn't have similar properties e.g. carbon and titanium

He mixed up metals and non-metals e.g. oxygen and iron

He didn't leave any gaps for undiscovered elements

1869 - Mendeleev arranged the 50 known elements into a table with various gaps.

Like Newlands', Mendeleev put the elements in order of atomic mass.

Medeleev found he had to leave gaps in order to keep elements with similar properties in the same group.

These gaps are very important as they predicted the propertiesof undiscovered elements. 

Group 1 are the alkali metals - these are silvery solids that are so reactive that they must be stored in oil and haandled with forceps.

As you go down the group, the metals become more reactive - this is because the outer electron is more easilylost as its further from the nucleus.

Also, as you go down the group, the metals have lower melting and boiling points.

Alkali metals have low densities... lithium, sodium and postassium are less dense than water.

All alkali metal atoms have one outer electron - keen to lose therefore, very reactive

Alkali metals form ionic compoumd with non-metals - they produce white compound that dissolve in water to form colourless solutions.

Li, Na, K react vigorously with water - float, move, fizz. This reaction produces hydrogen, K gets so hot it ignites it. Alighted splint indicates hydrogen by producing a 'squeaky pop' when hydogen ignites. 

They form hydroxides in water - alkaline solutions.

Elements in group 7 are known as halogens.

As you go down the group, the halogens become less reactive - harder to gain an electronas the outer shell is further from the positively charged nucleus.

Also as you go down the group, the elements have higher melting and boiling points.

The Halogens are all non-metals with coloured vapours - they exist as diatomic molecules - pairs of atoms

Halogens form ionic bonds with metals - as ions they are known as halides 

A more reactive halogen will displace a less reactive one from aqueous solution of its salt - remember trend in reactivity

Usual properties - good conductors of heat and electricity, dense, strong, shiny, not very reactive, higher melting points than group 1 metals (except mercury)

Transition metals often have more than one ion - for example, Fe(II) - gives green compounds and Fe(III) - gives red/brown compounds

Compounds of transition compounds are colourful due to the transition metal ion they contain

Transition metals and their compounds all make good catalysts - Iron used in Haber process for making ammonia, nickel is used in hydrogenation