Describe how sub-atomic particles make up the structure of the atom, location, mass and charge.
- Protons, in nucleus, relative mass = 1, charge +1
- Neutrons in nucleus, relative mass = 1, charge 0 * Electrons on energy levels. Relative mass=tiny, charge = -1
What was the first theory
about atoms?
Atoms were tiny spheres that cannot be divided
What was the plum
pudding theory?
Atom was a positive sphere with negative electrons embedded in it.
What were the results
and conclusion of the
alpha scattering
experiment?
Most alpha particles went straight through – most of the atom is empty space Some of the alpha particles were deflected – the centre of the atom has a positive charge A few of the alpha particles were deflected backwards – the centre of the atom is very tiny
What did Bohr discover?
Electrons orbit the nucleus at set distances
What did the scientists
first discover the nucleus
contained?
Protons
What did Chadwick
discover?
The nucleus also contained neutrons
- What are isotopes?
Isotopes of an element contain the same number of protons and electrons but a different number of neutrons.
How do you calculate
the relative atomic mass of an isotope?
Sum of (isotope abundance x isotope mass number) Divided by Sum of abundances of all the isotopes
Describe the main steps in the history of the periodic table
- Elements were placed in order of atomic weight * Early periodic table was incomplete and some elements were placed in the wrong group
- Medeleev left gap to ensure elements were placed in groups with similar properties. He predicted that new elements would be discovered to fit in the gaps. He also changed the atomic weight order if appropriate
State the properties of
group 1 – Alkali Metals
- Soft, low density, shiny, very reactive
- lithium + oxygen -> lithium oxide
- sodium + water -> sodium hydroxide + hydrogen
Explain why group 1 become more reactive as you go down
- Down the group, the atoms become larger
- Outer electron is further away from the nucleus and so there is less attraction
- Outer electron is more easily lost.
State the properties of
group 7 – The Halogens
- Non-metals, consisting of molecules of pairs of atoms * Further down the group the higher the boiling point
- More reactive halogen displaces a less reactive one
Explain why group 7
becomes less reactive as you go down
- Down the group the atoms become bigger
- Outer shell is further away from the nucleus so there is less attraction
- Harder to gain an electron
Why are group 0
unreactive?
They have a full outer shell of electrons
What happens to the
boiling points as you go
down group 0?
They get higher
