History of the periodic table Flashcards
What was Newlands law of octaves?
He arranged all the elements known at the time into a table in order of relative atomic mass, he found a pattern among the early elements.
What was the problem with Newlands law of octaves?
Some elements into groups which did not match their chemical properties.
What was Mendeleevs periodic table
He arranged them in order of atomic mass but arranged them so that groups of elements with similar properties fell into vertical columns in his table.
Why were there gaps left in Mendeleev periodic table?
The elements which belonged in the gaps had not yet been discovered.
What are the similarities and differences between Mendeleev and Newlands tables?
Similarities:
Ordered elements by atomic mass
Differences:
Mendeleev left gaps for other elements but Newlands only used the elements known at the time.
Mendeleev swapped some elements if it fitted the properties better but Newlines kept the order strictly in the atomic mass’s order.
How are elements organised in the modern periodic table?
By atomic number.
What is group 1 known as?
The alkali metals
What are the trends of the alkali metals as you go down?
As you go down:
Become more reactive,
Lower melting and boiling points
The alkali metals have low density
Why do the alkali metals become more reactive going down?
Because the outer electron is more easily lost because its further from the nucleus.
Name three alkali metals
Lithium, Sodium, Postassium, Rubidium, Caesium.
What bonds do alkali metals make?
Ionic bonds, because they want to lose the last electron in their outer shell.
What happens when alkali metals react with metals?
How can the product be tested?
They react vigorously,
produce hydrogen gas.
Hydrogen can be tested with a lighted splint, it makes a squeaky pop noise.
Whats the trends of Group 7 as you go down?
As you go down:
Less reactive,
Higher melting point,
Higher boiling point
Why do the halogens get less reactive going down?
Because its harder to gain an extra electron because the outer shells further from the nucleus.
What common properties of the halogens?
They are non-metals
They have low melting and low boiling points
They are brittle when solid
They are poor conductors of heat and electricity
They have coloured vapours
The molecules contain two atoms
