p4 Flashcards
1
Q
who came up with the plum pudding model?
A
- JJ Thompson
2
Q
describe the plum pudding model
A
- an atom with a ball of positive charge surrounded by electrons (which carry a negative charge)
3
Q
which two scientists conducted the alpha-scattering experiment?
A
- Marsden and Rutherford
4
Q
describe the alpha-scattering experiment
A
- Scientists took a piece of gold foil
- Scientists then fired POSITIVE alpha particles at the gold
- Most of the alpha particles passed straight through = so most of the atom is EMPTY SPACE.
- Sometimes, the alpha particles bounce straight back = the centre of the atom contains the MOST MASS.
- Some deflected slightly = the CENTRE OF THE ATOM HAS A POSITIVE CHARGE.
5
Q
what did Bohr discover?
A
- electrons orbit the nucleus
6
Q
what did James Chadwick discover?
A
- the nucleus contains neutrons
7
Q
in which order were protons, neutrons and electrons discovered?
A
- electrons, protons and neutrons
8
Q
- describe the nuclear model of the atom
A
- The model has a very small positively charged nucleus surrounded by outer electrons at a large distance from the nucleus. The protons and neutrons, which contain nearly all of the mass of the atom, are located in the nucleus at the centre of the atom.
9
Q
what is the radius of an atom?
A
- 1 x 10^-10 m
10
Q
what is the radius of a nucleus?
A
- 1 x 10^-14 m
11
Q
what kind of process is radioactive decay?
A
- random
12
Q
what are the units of radioactivity?
A
- Becquerels (Bq)
13
Q
what piece of equipment is used to measure radioactive decay?
A
gieger counter
14
Q
what is an alpha particle?
A
- helium nucleus (2 protons and 2 neutrons)
15
Q
what is the range of an alpha particle in the air?
A
- a few cm