2.1 - Atomic Structure & Decay Equations Flashcards
What is the charge of a proton?
+1.6x10⁻¹⁹C
What is the charge of a neutron?
0C
What is the charge of an electron?
-1.6x10⁻¹⁹C
What is the mass of a proton?
1.67x10⁻²⁷kg
What is the mass of a neutron?
1.67x10⁻²⁷kg
What is the mass of an electron?
9.11x10⁻³¹kg
What is the relative charge and mass of a proton?
charge = +1
relative mass = 1
What is the relative charge and mass of a neutron?
charge = 0
mass = 1
What is the relative charge and mass of an electron?
charge = -1
mass = 1/2000 (negligible)
What is specific charge?
The ratio of its charge to its mass.
What are the units for specific charge?
Ckg⁻¹
What is the equation for specific charge?
Specific charge = mass / charge
= Q / m
How do you calculate the specific charge of a nucleus?
specific charge = proton number x (1.60x10⁻¹⁹) / mass of all the protons + neutrons
How do you calculate the specific charge of losing an ion that has gained electrons?
specific charge = number of electrons gained x (-1.60x10⁻¹⁹) / mass of protons, neutrons and electrons
How do you calculate the specific charge of losing an ion that has lost electrons?
specific charge = number of electrons lost x (1.6x10⁻¹⁹) / mass of protons, neutrons and electrons
What is the proton number? (aka atomic number)
The number of protons in an atom (crazy right?!)
ᴬₚX
ₚ = proton number
(X = chemical symbol of element)
What is the nucleon number? (aka mass number)
Total number of protons and neutrons in nucleus.
ᴬₚX
ᴬ = nucleon number
(X = chemical symbol of element)
(also ᴬ - ₚ = number of neutrons)
What are isotopes defined as?
An atom (of the same element) that has an equal number of protons but a different number of neutrons. This makes them unstable.
What is isotopic data defined as?
The relative amounts of different isotopes of an element found within a substance.
What is an isotopic signature?
A set of ratios of the abundances of different isotopes in a sample.
What are the uses of isotopic data?
radioactive dating:
- Carbon-14 is a naturally occurring isotope common in living beings and goes under radioactive decay
- When the being dies the concentration of carbon-14 in its tissue reduces over time
- half-life = 6000 years and can be used to determine the age of dead plants/animals
What does the strong nuclear force do?
It keeps the parts of the nucleus together and therefore keeps it stable.
What is bigger, the electrostatic force or gravitational attraction?
The electrostatic force, by a lot.
When is the strong force repulsive?
Between 0 and 0.5fm (0.5 x 10⁻¹⁵)
When is the strong force attractive?
0.5fm to 3fm. (f = 10⁻¹⁵)
When is maximum attractive value for the strong force?
1.0fm (f = 10⁻¹⁵)
When does the strong force become 0?
After 3fm (f = 10⁻¹⁵)
What are the 4 fundamental forces?
- The strong force
- The weak force
- The electromagnetic force
- The gravitational force
What is the weakest force of the 4 fundamental forces?
The gravitational force.
Where does the electrostatic force come from in the nucleus?
The protons’ electric charge.
Where is alpha decay most common?
In large, unstable nuclei with too many protons.
What happens when an alpha particle is emitted?
From a structural perspective
2 protons and 2 neutrons are released.
So the proton number reduces by 2 and the nucleon number reduces by 4.
What is an alpha particle’s range like?
Very short, only a few cm through are and can’t penetrate paper.
What are 2 ways alpha radiation be observed?
- In a cloud chamber where the tracks left by alpha particles are shown.
- A Geiger counter, looking at the count rate drops
What happens in beta-minus decay?
A neutron turns into a proton emitting an electron and an electron-antineutrino.
So in equations, the proton number increases by 1 and the nucleon number stays the same.
What is the equation for beta minus decay?
n –> p + e⁻ + /Ve
What is an electron neutrino?
A type of subatomic particle with no charge and negligible mass which is also emitted from the nucleus.
In what decay are electron anti-neutrinos produced?
and also has a neutron decay into a proton
Beta-minus decay.
In what decay are electron neutrinos produced?
Beta-plus decay.
Why was the neutrinos existence hypothesised?
To account for the conservation of energy and momentum in beta decay.
What is the difference between antimatter and matter?
Antimatter particles are identical to their matter counterpart but the opposite charge.
What is the antimatter equivalent of an electron and what is its charge?
Positron.
Charge = +1
What is the antimatter equivalent of a proton and what is its charge?
Anti-proton.
Charge = -1
What is the antimatter equivalent of a neutron and what is its charge?
Anti-neutron.
Charge = 0
What is the antimatter equivalent of a neutrino and what is its charge?
Anti-neutrino.
Charge = 0
Are the masses and rest energies of antiparticles the same or different to matter particles?
The same.
What is annihilation?
When a particle meets its equivalent anti-particle they both are destroyed and their mass is converted into energy in the form of 2 gamma ray photons (high energy photons).
What is the minimum energy of one photon after annihilation?
The total rest mass energy of one of the particles -
Emin = hfmin = E
Emin = minimum energy of one of the photons produced (J)
h = Planck’s Constant (J s)
fmin = minimum frequency of one of the photons produced (Hz)
E = rest mass energy of one of the particles (J)
How is momentum conserved in annihilation?
The photons move apart in opposite directions.
