Owens Chemistry Unit 10 - Radioactivity

What are the 3 subatomic particles

protons, neutrons, electrons

Proton (p⁺)

Discovered by Rutherford

- Relative mass: about 1

- positively charged

Neutron (n⁰)

Discovered by Joliot-Curie/ James Chadwick

- Relative mass: about 1

- no charge

Electron (e⁻)

Discovered by JJ Thompson

- Relative mass: negligable\

- negatively charged

What keeps the nucleus together?

The strong nuclear force

What are the four fundamental forces

gravity, electromagnetic, strong nuclear, weak nuclear

Carrier particles for the four forces

Gravity: gravitons

Electromagnetism: photons (γ)

Strong nuclear: gluon

Weak nuclear: W and Z

Relationship between range of force and strength of forces

Gravity:

- Range: infinite

- Strength: weakest

Electromagnetism

- Range: infinite

- Strength: pretty weak

Weak nuclear:

- Range: pretty far

- Strength pretty weak

Strong nuclear

- Range: shortest

- Strength: Strongest

Strong Nuclear force

Force between protons and neutrons

- particle: gluons

- neutrons bring more strong force interactions to the nucleus

- you need the right amount of protons and neutrons to have a stable nucleus

Nucleons (N)

- total of protons and neutrons

- same as atomic mass/mass nimber

Atomic number (Z)

Equal to the number of protons found in an atom of an element

Mass number (A)

The total number of protons and neutrons in an atom (e.g. ¹²C)

Chemical symbol vs atomic symbol

Chemical symbol is just the element

- see picture for atomic symbol (picture doesnt include charge)

mass number vs average atomic mass

Mass number: total number of protons + neutrons in a nucleus

Average atomic mass: the weighted average of the masses of all naturally occurring isotopes of an element

What is the maximum amount of protons for a stable atom?

82: lead

Of the 3000+ known isotopes how many are stable?

around 250

Isotopes of hydrogen

Protium ₁¹H

Deuterium ₁²H

Tritium ₁³H

Alpha emision (α)

Alpha particle: ₂⁴He (helium nucleus)

Occurs when the atom is just too big (ex: past element 82)

- nucleus emits 2 protons and 2 neutrons

Properties:

- Charge: positive

- Mass: basically 4 protons (2 protons + 2 neutrons) (heavy) (doesnt penetrate much)

Beta decay (β⁻)

Beta (minus) particle: −₁⁰e⁻ (electron)

Occurs when there are too many neutrons (weak force problem)

- nucleus converts a neutron into a proton, releasing an electron

Properties:

- Charge: negative

- Mass: negligable (electron basically)

Positron emission (β⁺)

Beta (plus) particle: +₁⁰e⁺ (positron) (antimatter)

Occurs when there are too few electrons

- nucleus converts a proton into a neutron, releasing a positron

Properties:

- Charge: positive

- Mass: negligable

Gamma decay (γ)

Gamma ray: ₀⁰γ (light (really high energy))

Occurs when the nucleus is excited (indicated by *)

- nucleus releases a really high energy photon

half life

definition: the time it takes for half of the radioactive atoms in a group of identical atoms to decay

Equation: Amount of isotope remaining / Original amount of isotope = (1/2)ⁿ (where n is the amount of 1/2 lives)

Methods of radiation damage (bonus)

rads: amount of radiation

REMs: damage

RBE: damage