What did John Newlands do
He proposed the law of octaves after he ordered every element by its mass and realised that every 8th element seemed to have similar properties
Why did Newlands theory not catch on
-Several elements were placed in some spaces and it broke down further down the table they also deemed its relation to music laughable
How did Mendeleev’s theory differ from Newlands
-he left gaps
-predicted the properties of these theoretical elements and this increased his credibility when they were discovered
-swapped the order of several of Newlands
What is the difference between Mendeleev’s periodic table and the new periodic table
-addition of noble gases
-Mendeleev based his on atomic mass but now we use atomic number
-more groups added
What do elements in the same group/column have in common
Same number of electrons in outer shell
so similar properties
What do elements in the same row have in common
the same number of shells
What is the difference between oxides formed by metals and oxides formed by non-metals
Metal oxides are ionic and dissolve to give alkaline substances
Non-metal oxides are covalent and dissolve to give acidic solutions
What is the name for the group one elements
alkali metals
what is the name for the group 2 elements
alkali earth metals
What is the name for the group 7 elements
the halogens
What are the physical properties of the alkali metals
-soft and more so as you go down the group
-low density the top 3 can even float on water
-low melting and boiling points decreasing as you go down the group as the forces of attraction get weaker the further down the group you go
What are the chemical properties of group 1
very reactive so they are kept in oil to protect them from reacting with the oxygen in the air, when cut the surface tarnished within seconds forming an oxide coating
How do the alkali metals react with water
-floats in surface effervescence, hydrogen released, coloured flame if lit.
it leaves and alkaline solution and the reactivity decreases as you go down the group
Why does the reactivity of the group 1 elements increase as you go down the group
more distance between nucleus and outer electrons so weaker electrostatic forces of attraction so the electron is easier to lose
What are the features of group 1 compounds
ionic
white
soluble
colourless in solution
what kind of atoms are halogens
diatomic molecules and covalent bonds exist between these pairs of atoms
How do melting and boiling points change as you go down the group 7 elements
It is a simple molecular substance so the intermolecular bonds must be broken. The intermolecular forces are stronger as you go down the group so breaking then requires more energy
what do the halogens form when they react with other elements
halides
they are ionically bonded when reacted with metals and bond through direct combination
How does the reactivity of halogens change as you move down the group
It decreases, halogens must gain electrons so when there are fewer shells the nucleus is closer to the outer shell and therefore there are stronger electrostatic forces of attraction between it and the incoming electron. Further down the group the distance is further so the forces is weaker
How do displacement reactions work
When a halide is reacted with a more reactive halogen the more reactive element displaces the halogen in the halide
What are the colours of the first 4 halogens at room temperature
Fluorine- pale yellow
Chlorine-pale green
Bromine-orange yellow
Iodine-orange red
What are the physical properties of the halogens
-poor conductor of heat and electricity
-brittle and crumbly solids
-low melting points increasing down the group
-density increases down the group
-coloured
What type of structure is formed when halogens are reacted with metals or non-metals
Metals-ionic
Non-metals - covalent
What is the test for chlorine
damp blue litmus paper turns red and then bleaches
