atomic structure

Question 1

what is the history of atomic structure? (6 key scientists and dates)

Answer 1

1. democritus - greek philosopher
2. john dalton - 1808
3. jj thomson - 1897
4. rutheford - 1911
5. neils bohr - 1913
6. james chadwick - 1932

Question 2

what was the dalton model/idea of an atom? (4)

Answer 2

dalton thought that
1. matter is composed of tiny particles (atoms)
2. atoms of one element are alike in shape, size, weight but differ from atoms of other elements
3. during chemical changes, atoms combine formig molecules/compounds
4. during chemical changes atoms don’t change/ aren’t broken down

Question 3

what was jj’s thompson’s model/idea of an atom?

Answer 3

• found -ve electrons in the atom
• plum pudding model
  (electrons = negatively charged fruit, rest of atom= positvely charged pudding)

Question 4

what was the rutheford model/idea of an atom?

Answer 4

• rutheford fired alpha ray at a gold foil, found some where deflected
• tiny, positvely charged nucleus (most of the mass) surrounded by a cloud of negative electrons
• most of the atom is space

Question 5

what was bohr’s model/idea of an atom?

Answer 5

found that electrons orbit the nucleus in fixed shells (energy levels)

Question 6

what was chadwick’s discovery about atomic structure ?

Answer 6

discovered neutrons in the nucleus

Question 7

what is the structure of an atom?

Answer 7

• nucleus - protons and neutrons (positive charge) - take up most of the mass - very small compared to rest of atom
• shells/energy levels where electrons orbit the nucleus (negative charge) - take up most of the volume
• overall = no charge/ neutral

Question 8

relative mass and charge of
a) electron
b) neutron
c) proton

Answer 8

electron
mass = 1/1840
charge = -ve
neutron
mass = 1
charge = neutral
proton
mass = 1
charge = +ve

Question 9

what is the atomic number?

Answer 9

number of protons
(and also electrons since there is no overall charge so number of electrons = number of protons)

Question 11

what is the mass number?

Answer 11

mass of the nucleus (number of protons ad neutrons)

Question 12

what are isotopes?

Answer 12

• isotopes are atoms of the same element with the same number of protons and electrons, but a different number of neutrons in the nucleus
• eg Cl35 and Cl37

Question 13

how do you calculate the relative atomic mass/ RAM(Ar) ?

Answer 13

weighted mean of isotopic mass
(atomic mass1 x natural abundance) + (atomic mass2 x natural abundance) / 100
eg:
(35 x 75%) + (37 x 25%) / 100 = 35.5 - RAM of Cl

Question 14

what is the electric configuration for the first 3 shells?

Answer 14

2,8,8