strong force (or “strong nuclear force”): the force that holds the nucleus together. The energy comes from converting the mass defect to energy.
weak force: the force that makes protons and/or neutrons in the nucleus unstable. This can cause changes to the nucleus which change the element into a different one. (Yes, you could actually turn lead into gold this way!)
electromagnetic force: the force between electrical charges. If the charges are the same (“like charges”)—both positive or both negative—the particles repel each other. If the charges are different (“opposite charges”)—one positive and one negative—the particles attract each other.
gravity: the force that causes masses to attract each other. Usually only observable if one of the masses is very large (like a planet).
|
Force |
Relative Strength |
Effective Distance |
|
Strong |
1 |
Diameter of the nucleus |
|
Weak |
10−6 |
1/3 diameter of the nucleus |
|
Electromagnetic |
1/137 |
∞, but gets smaller as (distance)2 |
|
Gravity |
10−39 |
∞, but gets smaller as (distance)2 |
fundamental particle (or “elementary particle”): a particle that does not appear to be made of anything smaller. (“Where have I heard that before?”) Electrons are a fundamental particle, but protons and neutrons are not.
quark: one of the types of fundamental particle.
Quarks come in six flavors:
· up
· down
· top
· bottom
· charm
· strange
Protons & neutrons are made of up & down quarks. An “up” quark has a charge of +2/3, and a “down” quark has a charge of −1/3.
proton: a subatomic particle made of two up quarks (+2/3) and one down quark (−1/3):
↑↑ ↓
The net charge on a proton is:
2(+2/3) + (−1/3) = +1.
neutron: a subatomic particle made of two down quarks and one up quark:
↑ ↓ ↓
The net charge on a neutron is:
(+2/3) + 2(−1/3) = 0.
Beta (β) radioactive decay occurs when the weak force changes the spin on one of the quarks in a proton or neutron. In the most common form (β− decay), the spin goes from “down” to “up,” which turns a neutron into a proton.
Because of the law of conservation of charges (the total charge has to be the same before and after any change), any change that produces a positive charge has to also produce a negative charge. The way this happens is that when the quark changes its spin, the neutron turns into a proton plus a particle called a “W− boson.” The W− boson then splits into an electron and a neutral fundamental particle called a neutrino. Both the electron and the neutrino are ejected from the nucleus of the atom at high speed.