Atomic Structure Flashcards
What is the radius of an atom?
1x10^-10 m
Charges of the subatomic particles
proton= +1
neutron= 0
electron= -1
Masses of the subatomic particles
proton= 1
neutron= 1
electron= 0
What happens to electrons when something absorbs electromagnetic radiation?
the electrons are moved to a higher energy level, further from the nucleus
What happens to electrons when something emits electromagnetic radiation?
the electron drops to a lower energy level, closer to to the nucleus
Positive ion
when an atom has LOST an electron
Negative ion
when an atom has GAINED an electron
What do all atoms of an element have the same of?
proton number (atomic number)
Mass Number
number of protons and neutrons in a nucleus
Atomic Number
Number of protons
Isotopes
atoms of an element that have the same number of protons, so are from the same element, but they have a different number of neutrons
Plum pudding model
the atom is a ball of positive charge with negative electrons embedded in it.
Gold Foil Experiment: Results
most passed straight through
some were deflected so they must have been repelled by the same charge that the alpha particle carried
the repelling charge must have been heavier than the alpha or it would have passed straight through
Gold Foil: Conclusions
mass of the atom in in a central, positively charged nucleus
the electrons surround the nucleus
Role of Neils Bohr
adapted the model by suggesting that electrons orbit the nucleus at set distances
The results of the later experiments
the positive charge of the nucleus can be divided into a whole number of smaller particles, each with the same amount of positive charge, commonly known as protons
Role of James Chadwick
1932
carried out a number of experiments which provided evidence that in the nucleus there was also a particle called the neutron
Which type of nuclei, decay, and why?
Unstable nuclei give out radiation to become more stable
Activity
the rate at which something decays
What is activity measured in?
Becquerels
One Becquerel=
One decay per second, one count rate per second
Count rate
the number of decays per second
3 types of nuclear decay
alpha, beta, gamma
Alpha
- 2 protons, 2 neutrons
-strong ionising power
-absorbed by a few cm of air/paper
-can cause damage to living cells