C3 Flashcards
Who was Newlands?
A chemist who noticed every 8th element had similar properties and created Newlands octaves
Why was Newlands work criticised?
- his groups contained elements that didn’t have similar properties
- he mixed up metals and non-metals
- he didn’t leave gaps for undiscovered elements
What did Mendeleev do?
arranged the elements in order of atomic mass (like Newlands) but left gaps so that elements with similar properties were in the same vertical column. He also predicted properties of undiscovered elements
elements in the same group have the same…
number of electrons on their outer shell
if the electron is far from the nucleus the force of attraction is…
weak, especially if the electron is shielded by other elctrons
the combination of increased shielding and distance means that…
an electron in a higher energy level is more easily lost as there’s less attraction from the nucleus.
This is why group 1 is more reactive as you go down the group
what are the properties of alkali metals (group 1 metals)?
low density and 1 outer electron
As you go down group 1:
- become more reactive
- lower melting and boiling points
What happens when group 1 metals form ionic compounds with non-metals?
produces white compounds that dissolve to form a colourless solution
What happens when group 1 metals react with water?
produce hydrogen gas, they float and fizz alot
What are the first 3 group 1 metals?
lithium, sodium, potassium
what are the properties of the halogens (group 7)?
non-metals with coloured vapours
Describe fluorine
very reactive, poisonous yellow gas
Describe chlorine
fairly reactive, poisonous dense green gas
Describe Bromine
dense, poisonous red-brown volatile liquid
Describe Iodine
dark grey solid or purple vapour
What happens as you go down group 7?
- less reactive
- higher melting point
- higher boiling point
What happens when halogens bond with metals?
they form 1- ions called halides
What are the properties of transition metals?
- good conductor of heat + elctricty
- very dense, strong and shiny (more than group 1 metals)
- less reactive than group 1 metals
- much higher melting points than group 1 metals
What is the reactivity of an element?
how easily its atoms lose or gain electrons
What is soft water?
it easily lathers with soap and contains dissolved sodium ions
What is hard water?
contains dissolved magnesium and calcium ions and produces scum and scale when ions react with soap or when the water is heated
What is scum?
formed when the calcium ions in hard water displace the sodium stearate to form calcium stearate
What is scale?
a thermal insulator and is formed when hard water is heated. it collects in pipes, boilers and kettles.