The Nuclear Atom Flashcards
(22 cards)
Explain the alpha particle scattering experiment.
Consists of alpha particles fired at thin gold foil and a detector on the side to detect how many particles are deflected at different angles.
What does the alpha scattering experiment provide evidence for?
The structure of an atom.
What are the results of the alpha particle scattering experiment?
- Most alpha particles go straight through the foil
This guests the tom is mostly empty space. - Some are deflected at small angles < 10
This suggests there is a positive nucleus at the centre of the atom.
-Very small number bounce back at angles > 90
This suggests the nucleus is extremely small and the mass is concentrated.
- Therefore atoms consist of a small, dense, positively charged nucleus.
What makes an atom stable?
An equal number of protons and electrons.
What’s the average ratio of an atom to its nucleus and what’s their relative diameters?
Atom is approximately 100,000 x bigger than its nucleus.
Diameter of atom is approx: 1(x10)^-10m
Diameter of nucleus is approx: 1(x10)^-15m
What is the closest approach method?
Since some particles rebound in the scattering experiment, this shows there are electrostatic repulsion between the alpha particles and the gold nucleus.
Kinetic energy is at max when furthest away from the gold, and Potential energy is at its max when at the limit of closest approach (r).
This means that you can equate 1/2mv^2 and (Qq)/4(pi)(exilum0)r.
What’s the top number on a chemical symbol?
The nucleon number, the number of protons + the number of neutrons.
What’s the bottom number on a chemical symbol?
The proton number, the number of protons (same as the number of electrons)
What’s an isotope?
An atom that has its usual number of protons but a different number of neutrons.
Isotopes are…
Unstable, they emit radiation to achieve a more stable form.
What do neutrons affect in an element?
The elements mass, not its charge.
Which number is 12 in carbon-12?
The nucleon number (top number) (protons + neutrons)
What forces are present in the nucleus?
-Electrostatic forces between the protons due to the charge (repulsive).
-Weak gravitational forces due to the protons mass.
-The strong nuclear force that hols the nucleus together (attractive)
How does the strong nuclear force keep the nucleus together?
Holds quarks together.
What’s the range of the strong nuclear force?
- Repulsive before a separation of approx 0.5fm
- Attractive till approx 3.0fm
-Max attraction of approx 1.0fm (at typical nuclear separation)
- SNF is 0 after 3.0fm
What is r0?
1.2fm or 1.2(x10)^-15 m
What happens to increase the nuclear radius?
More nucleons added.
What’s the equation for the nuclear radius?
R= (r0)(A^(1/3))
Where R is the nuclear radius, r0 is a constant (1.2fm) and a is the nucleon number.
What’s the relationship between nuclear volume and mass of nucleus?
volume is directly proportional to the nucleon number and therefore also the mass.
What’s the equation for the mass of a nucleus?
Mass = Au
Where A is the nucleon number and u is the atomic mass unit.
Whats an equation for the nuclear volume?
V= 4/3(pi)(r0 cubed)A
Where A is the nucleon number and r0 is a constant.
Whats the equation for the nuclear density and what does it show?
ρ= (3u)/(4(pi)(r0 cubed))
This shows nuclear density is constant and therefore the nucleons are evenly separated throughout the nucleus whatever its radius.
