history of periodic table Flashcards
in the 1800s what were the two ways of categorising elements?
- physical and chemical properties
- relative atomic mass
what did they have no idea about in the past?
protons and electrons
newlands law of octaves?
- in 1864 every 8th element had similar properties
- the pattern broke down on the third row with titanium and iron
- left no gaps
why was newlands law of octaves criticised?
- groups had elements with different properties in (carbon and titanium)
- mixed non metals and metals together
- didn’t leave gaps for undiscovered elements
dimitri mendeleev
- in 1869 he put elements in order of atomic mass
- but he left gaps for elements with similar properties in same vertical group
- when new elements were found they fitted the pattern
the modern periodic table
- electron with a high energy level is easily lost as there is less attraction
- high energy level elements are less likely to gain electrons as there is less attraction from they nucleus
as you go down the column, group 1 metals are…
more reactive
as you go down the column, group 7 elements are…
less reactive
what did mendeleev do that was convincing?
he left gaps which newly discovered elements fit into perfectly
what did they discover in the late 19th century?
protons, neutrons and electrons. the periodic table matches well.
in the modern periodic table how are elements arranged?
by their electronic structure which predicts their chemical properties
when is attraction less?
when there are a lot of inner electrons, as they get in the way of nuclear charge also known as shielding
