Mr. Bouyer

Day 1 | Day 2 | Day 3 | Lab | Vocabulary Test

Subatomic particle Atomic number Atomic mass Isotope Antimatter Quantum physics Quark	Fermion Lepton Hadron Baryon Boson Photon Gluon	Electromagnetic force Strong nuclear force Weak nuclear force Gravity GUT TOE Black hole

	Subatomic Particles: the particles composing atoms.

What do the letters in the equation above mean?

Before the advent of accelerators (50+ years ago), all matter was thought to be made up of only three particles: protons, neutrons, and electrons. As the power of these "machines" has grown, our understanding of atomic structure has changed. The current atomic theory includes over 50 particles! Explore the Particle Adventure to find out more about the our understanding of subatomic particles.

Atomic number:

Always expressed as a whole number on the periodic table.

The atomic number equals the number of protons in an atom. Since + and - charges are normally equal, it is also the number of electrons.

Atomic mass:

Almost always expressed as a decimal fraction on the periodic table.

The mass number of an atom is equal to the sum of the protons and neutrons in its nucleus. For our class, round off the mass number on the periodic table to the nearest whole number.

Isotopes:atoms of the same element with different numbers of neutrons.

The mass number for an element on the periodic table represents the average for all the isotopes in a sample of the element.

Look at the example below: notice that Carbon-12 has 6 neutrons, while Carbon-14 has 8 neutrons.

Number of neutrons in an atom = (mass number, as a whole number) - (atomic number)

Build an atom on this webpage

Atomic numbers & masses can be found on this alphabetical list or this periodic table

In-class Assignment 081:
This assignment must be turned in by the end of class today to receive credit.
Scoring criteria

1. How many protons are in each of these atoms?
   1. carbon
   2. iron
   3. bromine
   4. gold
   5. uranium
2. How many electrons are in each of these atoms?
   1. helium
   2. chlorine
   3. sodium
   4. mercury
   5. barium
3. How many neutrons are in each of these atoms?
   1. copper
   2. lead
   3. silver
   4. iodine
   5. tin

Day 2

Understanding the quark model of the atom is more in the field of quantum physics than chemistry. But a good chemist has a basic understanding of the key points of the model presented on this page.

Chemistry Career Planner

Quantum physics describes the behavior of the world on very small scales, the scale of molecules, atoms, and below. Max Karl Ernst Ludwig Planck (1858-1947) contributed to the foundation of quantum physics. He has been honored by adding his name to the following measurements related to the scale (Planck scale) of the quantum world. Planck density: the density of matter where 1 Planck mass occupies a volume of 1 Planck length across - roughly 1094 g/cm3, 1060 times the density of an atomic nucleus. Planck length: the smallest measurement of length that has meaning. Determined by the relative sizes of the constant of gravity, the speed of light, and Planck's constant. It is roughly 10-33 cm, about 10-20 times the size of a proton. Planck mass: the mass of a hypothetical particle which would have an equivalent wavelength, according to quantum theory, equal to 1 Planck length. It is roughly 10-5 gram. Planck time: the smallest measurement of length that has meaning. Determined by the time it would take light to cross a distance equal to the Planck length. It is roughly 10-43 second. Planck's constant, h: relates the particle nature of a quantum entity to its wave nature through the equation E=hf. Planck's constant has a value of 6.626 X 10-27 Joule seconds.

Quarks were "invented" by Murray Gell-Mann and George Zweigof Caltech in 1964. The name "quark" apparently originated in the phrase "three quarks" used by James Joyce in his novel Finnegans Wake. In science, the first person to make a discovery or propose a new theory gets to name the discovery or theory. The odd choice of names related to quarks might be attributed to the time of the discovery. In 1964, California was the center of the "hippie" experience. Could the odd names related to quarks mean that Gell-Mann and Zweig were Hippies?

The idea of quarks was not taken seriously at first. But accelerator experiments in the early 1970s began to provide experimental evidence supporting their existance. The quark model is the best theory we have today to describe the structure of atoms and molecules.

Quarks have "flavors" and "charges"
• Up, + ²/₃
• Down, - ¹/₃
• Charm, + ²/₃
• Strange, - ¹/₃
• Top, + ²/₃
• Bottom, - ¹/₃
All quarks have a spin equal to ¹/₂
Quantum chromodynamics

There are three varieties of quark colors related to force: red, green, and blue.

Quark mass

So small that they could probably travel through a mile and a half thickness of lead without hitting another particle.

Quark confinement:

Quarks can not exist by themselves. Quarks must be bound to other quarks by the exchange of gluons.

• Three quarks (a triplet) inside hadrons.
• Quark-antiquark pairs inside mesons.

Not all quarks are subatomic particles.

Subatomic particles based on quarks:

Fermions: quarks and leptons.

Leptons: "lightweight" elementary particles not composed of quarks. They include:

Electron

This particle has a mass of 9.1 X 10 ^-31 kilograms, an electric charge of -1.6 X 10 ^-19 coulombs, and a spin of ¹/₂.

Muon

This particle is identical to the electron except its mass is 206.77 times greater. Muons are unstable, with a half-life of 2.197 microseconds.

Tau

Another "heavy" electron with a half-life of only 3 X 10 ^-13 seconds.

3 Types of Neutrinos

Each neutrino has zero charge, a spin of ¹/₂, and a mass between 1 millionth and 1 hundred-thousandth of the mass of an electron.

• electron neutrino
• muon neutrino
• tau neutrino

Hadrons: "massive" particles composed of quarks.

Baryons: composed of three quarks.

Baryons compose "everyday" matter.

Proton:
• Composed of two up quarks and one down quark.
• Protons have a mass of 1.67 X 10 ^-27 kilograms, a charge of 1.6 X 10 ^-19 coulombs, and a spin of ¹/₂.
Neutron:
• Composed of two down quarks and one up quark.
• Neutrons have a mass of 1.67 X 10 ^-27 kilograms, zero charge, and a spin of ¹/₂.

Mesons: composed of a quark and an antiquark.

Mesons are involved in the interactions which hold nucleons together in an atomic nucleus.

• Pion (pi-meson)
• Kaon (K-meson)

Bosons: "force carriers"

It is the exchange of these particles between fundamental particles that allows the formation of the more massive particles. Bosons are not conserved - for example, billions of photons are created every time you turn on a light, and disappear when they are absorbed by atoms.

• Photon - massless, no charge, electromagnetic force carrier.
• Gluon - massless, no charge, strong nuclear force carrier.
• W ⁺, W ^-, and Z ^o - massless, weak nuclear force carriers with indicated charge.
• Graviton - massless, no charge, gravity force carrier.
  • The graviton is the only force-carrying particle that has not been observed, either directly or indirectly.

Antiparticles: particles that have exactly the same mass but opposite charges.

Leptons and quarks have anti-particles.
Bosons do not have anti-particles.

Today's atomic model explains the structure of atoms using 6 types of quarks, 6 types of leptons, and 4 types of force carriers.

Test Your Concept Understanding: What are the flavors of quarks? Using particle charge, explain why a proton must be composed of two "up" quarks and one "down" quark. Only one particle described on this page has never been observed. Which particle is it? Give one possible reason why the particle in question #4 has not been observed?

Physical Science

Energy = Mass times the Speed of light squared.

Antimatter is composed of antiparticles.
Antiparticles are just like regular subatomic particles except they have opposite charges.