C3.1 Periodic Table Flashcards
What were John Newlands’ Octaves?
Law of octaves 1864
Arranged all elements known at the time into order of relative atomic mass
Found that each element had similar properties of the element 8 places in front
Placed them in 8 verticles columns of three, the similar elements in each columns known as groups
What were the limitations of Newlands’ octaves?
By strictly ordering to atomic mass, Newland placed some elements in groups that did not match their properties eg iron (metal) in the same group as oxygen (non metal)
Some scientists consequently did not accept the theory
Who published the first periodic table in 1869?
Dmitri Mandelev
Why was Mandelevs table more successful than newlands?
Although he also ordered it by RAM, he realised that physical and chemical properties were linked to the RAM of the element in a periodic way.
Like Newland, he ordered it in groups (periods) but he left gaps where undiscovered element would fit in
He estimated the RAMS of these elements and their properties and turned out to be right!
What were the similarities between Mandelevs and Newlands tables?
- Ordered elements by weight
- Elements grouped by properties
What were the differences between Mandelev and Newlands tables?
- Newland only included elements that were known at the time
- Mandelev swapped the order of the elements to fit the groups better
- Newland was critisized, Mandelev was appreciated
How did the discovery of Protons, neutrons and electrons affect Mendelevs table?
The elements could now be ordered by their atomic number rather than weight which was more accurate
Who proposed using the atomic number rather than weight to order the periodic table?
Henry Mosely 1913
What does the group (column) in the periodic table represent?
All elements in a group have the same / similar properties due to the fact they all have the same amount of electrons in their outer shell
The group number is how many electrons are in the outer shell
What do the periods (rows) in the periodic table represent?
The periods have the same amount of shells occupied with electrons
What are the properties of the group 1 alkali metals?
- Very reactive (cannot contact air or water)
- Soft
- Low densities
- React quickly with water to create hydroxides+hydrogen
- Their hydroxides dissolve in water to create alkaline solution
In general :
Group 1 metal + water = G1 metal hydroxide + hydrogen
What are the physical and chemical trends of group 1 metals?
- Low melting and boiling points that decrease further down the group
- Reactivity increases further down the group
- React with non metals to form ions
What are the properties of the transition metals?
- High melting point
-Low / medium reactivity - Strong / hard
-High density
-Coloured compounds
Can act as catalysts
What are the properties of the group 7 halogens?
- Toxic ( this means they can sterilise and act as antispetics)
- non metal
- low melting and boiling points
- Brittle when solid
- Poor conductors of heat and electricity
- coloured vapours
- Molecules are diatomic (contain two atoms!)
What are the trends in group 7?
-The melting and boiling point increases further down the group
- The colour grows darker down the group
-Less reactive as you go down the group
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