Unit 3: 1 - The Periodic Table Flashcards
Why did scientists use atomic weights to classify elements in the 19th century?
Because they did not know the structure of the atom.
What was Newlands law of octaves?
A law that stated that similar properties are repeated every 8th element.
Why was Newlands law of octaves eventually rejected?
Because at the time, he could put the 62 known elements into 7 groups, but after calcium their properties did not match.
Who set out the basis for the early periodic table?
Dmitri Mendeleev.
Why are elements lower down in groups (e.g. group 1) generally more reactive?
As the electrons are further away from the nucleus, the electrostatic forces of attraction are weaker, so the structure can easily be changed.
What are group 1 metals?
Alkali metals.
What are the transition elements (or transition metals)?
The elements between groups 2 and 3.
What properties do transition metals (except for mercury) have relative to alkali metals?
Higher melting and boiling points.
Describe the reactions that transition metals/elements have with water and oxygen?
None or very slow.
What are the properties of halogens?
Small molecules with 7 elements in their outer shell, that have low melting and boiling points (which increase as they go down the group) and usually exist in pairs of atoms.
Properties of group 1 metals (4)
Low density, reacts with metals to form ionic compounds (with any element they bond to it is a +1 charge), reacts with water (releasing hydrogen), forms soluble hydroxides.
As you move down group 1, … (2)
The more reactive the element and the lower the melting/boiling point.
Properties of group 7 (halogens) (5)
Poor conductors, poisonous, coloured vapours, reacts with metals to form ionic compounds, makes halide ions with a -1 charge.
The further down group 7 you go, … (2)
The less reactive the element, the higher the melting and boiling points.
