Atomic structure and periodic table Flashcards
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)/ Sum of abundances of all the isotopes
Example of calculating relative atomic mass:
Copper has two stable isotopes. Cu-63 has an abundance of 69.2% and Cu-65 has an abundance of 30%. Calculate
the relative atomic mass of copper to 1 decimal place
Relative atomic mass = (69.2 x63) + (30.8 x 65)/69.2+30.8 = (4359.6 + 2002)/100 = 6361.6/100 = 63.616 = 63.6
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
• Mendeleev 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
