1.1. Atomic theory

Question 1

the Rutherford experiment

Answer 1

• nucleus is positive (positive Alpha particles repulsed)
• nucleus is the smallest but the heaviest (p+ and n^0) part of the atom (atom is mostly empty space)

Question 2

Bohr’s atom model

Answer 2

• electrons are moving (rotating) round the nucleus (centripetal force resists the attraction from nucleus - no implosion)
• electrons have specific energy levels
• electrons can jump to higher levels of energy only if they gain sufficient E

Question 3

Electrons will try to get back from the excited state by emitting extra energy and jumping to the lower shell because…

Answer 3

…the ground state is stable, unlike the excited state.

Question 4

line spectrum

Answer 4

spectrum of specific wavelengths at which electrons emit light (hydrogen emission line spectrum)

Question 5

Lower E=…

Answer 5

…higher wavelength and red light.

Question 6

Higher E=…

Answer 6

…lower wavelength and purple light.

Question 7

Jump of e- from any to ____ shell is always visible on the emission spectrum.

Answer 7

second

Question 8

Why do “relative” quantities never have units?

Answer 8

Because the actual value has been divided by a certain standard value, and since both have the same unit, it cancels out.

Question 9

Electrons are ___ times ___ than protons.

Answer 9

2000, lighter

Question 10

atomic number

Answer 10

• Z
• number of protons (& electrons)

Question 11

mass number

Answer 11

• A
• number of protons and neutrons

Question 12

radioisotope

Answer 12

• an isotope with an unstable nucleus
• excess energy
• undergoes radioactive decay (emits gamma rays and/or subatomic particles (ionizing radiation)
• can occur naturally but can be artificial

Question 13

use of radioisotopes:

Answer 13

1) radiocarbon dating
- radiometric dating method using naturally occurring C-14
2) nuclear medicine (radiotherapy)
medical use of ionizing radiation (Co-60)
3) medical tracing
iodine-125, iodine-131 used for single photon emission computed tomography (SPECT) imaging and positron emission tomography

Question 14

dangers of radioisotopes

Answer 14

• radioactive contamination/pollution
• radiation poisoning

Question 15

the actual mass of a proton/neutron

Answer 15

1.67*10^-24 g

Question 16

why is C-12 used as a reference atom

Answer 16

has exactly the same relative mass to its actual mass (up to 7 decimal places) - also a very common material

Question 17

1 atomic mass unit (amu) is defined as 1/12th the mass of a…

Answer 17

…carbon-12 atom.