Development of the periodic table

what is a triad?

3 elements where the middle mass is the mean of all 3

what physical property was used to organise the elements?

atomic mass

what was interesting abt the middle element when the 3 elements were organised in triads?

it was the mean mass of all 3

what was the issue with this triad organisation?

not all the elements fitted

how did Dalton represent each symbol in the earliest periodic table?

with a symbol / picture in a circle

were the symbols organised at all?

metals and non-metals together

what 2 things did Mendeleev notice was wrong with Newland’s previous octave periodic table?

he assumed all elements had been discovered, thought the law of octaves would work throughout the table with 7 elements in every row

what physical property was used to organised the elements?

ordered by increasing atomic mass

why did Mendeleev leave gaps in his periodic table?

for undiscovered elements

why did elements such as telllurium and iodine need to be swapped around?

so they were in groups with elements that had similar properties

what physical property was used to organise the elements?

increasing atomic mass

what did Newland notice about every 8th element when he organised them?

similar properties

what issues were there with this method?

stopped working after calcium

how is the modern periodic table organised?

rows in order of increasing atomic number

how is this different to all the other attempts at organising?

use the atomic number, putting elements in groups by reactivity

How does this agree with Mendeleev swapping Te and I around?

they ended up in correct groups