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Sub-Atomic Particles & the Earliest Forms of Matter
2012
1) Reviewing Basic Atomic Structure - All matter is made up of atoms.
Atoms in turn are made up of 3 general types of particles:
1) Protons
1)
Protons -
2) Neutrons
3) Electrons
have a positive ( +1 ) electrical charge
have a mass defined as 1 atomic mass unit (1 a
Atomic symbol =
or ( 1P1 )
m
u )
A single proton is the same as a Hydrogen ( 1H1 ) nucleus.
2)
Neutrons - have a neutral ( 0 ) electrical charge
also have a mass defined as 1 atomic mass unit (1 a
Atomic symbol =
or ( 0n1 )
m
u )
In other words, protons and neutrons have the same mass, but different charges.
Protons and neutrons are both found in the nucleus,
so protons and neutrons both belong to a group of particles called
nucleons.
Each element has its own unique number of protons. The number of protons an element
contains is called the element’s atomic number (the element’s “I.D. number”).
3)
Electrons - have a negative ( -1 ) electrical charge are almost
weightless ( mass = =
Atomic symbol =
0 amu )
or ( -1e0 )
Electrons orbit around the nucleus at nearly the
speed of light (very fast). Since electrons have
almost no mass, virtually all of the mass (weight)
of an atom is found in the nucleus. Adding up
the number of protons and neutrons in the nucleus, you get the atom’s
mass number (related to atomic mass and atomic weight).
Atoms of the same element always have the same atomic number ( # of protons ),
but may have different mass numbers. These are called isotopes.
Isotopes have the same number of protons, but different numbers of neutrons.
2)
Even Smaller Sub-Atomic Particles - the Earliest Forms of Matter
Pg. 2
Matter is also made up of two other types of particles: 1) Quarks and 2) Leptons.
1)
Quarks - trapped inside of larger particles such as protons and neutrons. Quarks have
not been found by themselves naturally since the first seconds of the Big Bang.
Ordinary matter contains up (
) & down (
) quarks. (There are also charm,
strange, top and bottom quarks: these larger quarks are only found today in cosmic rays
coming in from outer space & inside particle accelerators.)
= Up Quark (
) + 2/3 charge
A proton consists of
) –1/3 charge
= Down Quark (
2
up quark(s) and
1
down quark(s).
The total charge on the proton = +2/3 + +2/3 + -1/3 =
+1
The first formation of protons formed during the Big Bang was also
the first appearance of Hydrogen nuclei:
Hydrogen atoms are all very, very old.
A neutron consists of
1
up quark(s) and 1
down quark(s).
The total charge on the neutron = +2/3 + -1/3 + -1/3 = 0
This is why protons and neutrons have the same mass but different
charges.
2)
Leptons - are tiny, virtually weightless particles that often travel on their own at very
high speeds (approaching the speed of light):
1)
Electrons ( -1 charge ) play a big role in chemical reactions, light & electricity
2)
Electron Neutrinos (no electrical charge) - don’t interact with other forms
of matter very often. They come streaming in from space all the time. Billions of
neutrinos have flown through your body while you have been reading this page!
Atomic Structure of the Second and Third Elements
This is a Helium Nucleus
Symbol = 2He4
Atomic Number =
2 .
4 ..
This is a Lithium Nucleus
Mass Nuimber =
Symbol = 3Li7
Atomic Number =
Mass Number =
7 .
3 .