C2 Year11 Revision Flashcards
(27 cards)
John Dalton’s Atomic Theory
believed that atoms could not be divided, but were rearranged in chemical reactions
John Newland’s periodic table
noticed a repeating pattern every 8 elements and suggested elements were found in ‘octaves’
Disadvantages of Newland’s ideas
The octaves only work for the first 20 elements.
Order of elements on historic periodic table
Elements were ordered by atomic weight
Order of elements on modern periodic table
Elements are ordered by atomic number
Dmitri Mendeleev’s ideas
Ordered elements by atomic weight BUT changed the order/left gaps to keep elements with similar properties in the same column
Advantages of Mendeleev’s ideas
He was able to predict the properties of elements in the gaps.
Group
A vertical column of elements with the same number of outer shell electrons
Period
A horizontal row of elements with the same number of electron shells
Name for Group 1 elements
alkali metals
Pattern in reactivity down group 1
reactivity increases
Appearance of group 1 elements
shiny when cut, but tarnish as they react with oxygen
Metal + water –>
metal hydroxide + hydrogen
Observations: Sodium + Water
Floats on surface, melts into a bowl, fizzes, moves on the surface of the water
Observations: Lithium + water
Floats on the surface of the water, moves around and fizzes
Observations: Potassium + water
Floats on the surface of the water, moves around, fizzes, melts into a ball, burns with a lilac flame.
When group 1 elements react
they lose their outer electron
Potassium is more reactive than sodium because
atomic radius increases, shielding increases, nuclear attraction decreases, easier to lose an electron
Name of Group 7 elements
The halogens
Group 7 elements have similar chemical properties
because they all have 7 outer shell electrons
Pattern in melting points and boiling points down group 7
melting and boiling points decrease
Pattern of reactivity down the halogens
they get less reactive
Reason for patterns in reactivity
larger atomic radius, more shielding, less nuclear attraction, harder to gain a reaction
Group 7 elements react by
gaining 1 electron
