Atomic Structure

Basic and Beyond

What are the 3 major parts of an atom?

Protons

Electrons

Neutrons

Where is each located?

What are the charges on each basic part?

Protons

Who discovered the proton? What experiment did he use?

Protons are positively charged particles found in the atomic nucleus. Protons were discovered by Ernest Rutherford.

Protons have a mass. We designate this mass as 1 amu (atomic mass unit).

Protons determine the atomic number and thus the identity of the substance.

Can protons be broken down?Experiments done in

the late 1960's and early 1970's showed that protons are made from other particles called quarks.

Protons are made from two 'up' quarks and one 'down' quark.

Neutrons

Why would a neutron be hard to discover?

Neutrons are uncharged particles found in the atomic nucleus.

They have a mass of 1 amu

Isotopes result when neutron number changes

The decimals in the atomic mass are from the AVERAGE of the isotopes.

Neutrons were discovered by James Chadwick in 1932.

Isotopes

Example:

http://education.jlab.org/glossary/isotope.html

Can Neutrons Be Broken Down?

• Experiments done in the late 1960's and early 1970's showed that neutrons are made from other particles called quarks. Neutrons are made from one 'up' quark and two 'down' quarks.

The Nucleus

The nucleus contains most of an atom's mass. Why?

The nucleus is the central part of an atom. It is composed of protons and neutrons.

Unlike in a living cell, the nucleus of an atom is not a physical thing. It is the name for the area that holds the protons and neutrons.

What forces hold the atom together?

Weak Force works with quarks and

leptons and decides how flavors change

helps stabilize nuclei through beta decay

shorter distances than the strong force!

Gravity

Since this binds matter together based on mass, we think this plays no role in atoms

Electromagneticlikes repel,

opposites attract (+ or -)

Strong Force interacts with hadrons or nucleons so the protons and neutronsbinds them togetherworks only at distances smaller than 1 quadrillionth of a meter!!!

Electrons

Who discovered electrons? What experiment was used? Why were they easy to discover?

Electrons are negatively charged particles that surround the atom's nucleus.

The mass of an electron is so small that it is called “zero”.

Electrons determine chemical properties of the atom.

Electrons are arranged in orbitals that are part of probability clouds.

What is the Electron Cloud Model?Diagram 1:

So subatomic particles are themselves made of smaller

particles!• Subatomic particles composed of fast

moving points of energy called quarksQuark Calculations

(for protons and neutrons)

Each proton is 2 up quarks and 1 down quark

2(2/3) – 1(1/3) = 4/3 – 1/3 = 3/3 or +1

Each neutron is 2 down quarks and 1 up quark

2(-1/3) + 2/3 = 0

Each electron is composed of 2 down quarks

3(-1/3) = -1

What is a quark, anyway?

The are held together by the strong force.

fundamental particle which possesses electric charge and 'strong' charge.

They combine in groups of two or three to form mesons and baryons

There are several kinds of quarks

quarks come in six different species (physicists call them 'flavors')

each flavor has a unique mass.

So, are there other characteristics of quarks?

The two lightest are

'up' and 'down' quarks

They combine to form protons and neutrons.

The heavier quarks aren't found in nature and have so far only been observed in particle accelerators.

Can we get smaller?

Fermions

Bosons

Leptons

Hadrons

And more

So we can catagorize

And get smaller

But quarks are still the smallest for now

Can things get even smaller?

Higgs boson

Neutrino

And more are hypothesized sub sub sub particles!

Still looking for evidence for these. . .

Why are sub subatomic particles important?

Could lead to many things in the future: energy, new elements

Predict properties such as nuclear decay

Explain types of nuclear decay

Help us to understand organization of matter

How are new particles discovered?

How do accelerators work?