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The Amazing Atom
The Amazing Atom
Hydrogen H
Most common element (atom) in the
Universe around 74% (nearly 3/4) of all
matter in the universe is hydrogen.
Hydrogen is the building block of all
matter – used by stars to make all other
atoms.
1 proton in its nucleus
The Amazing Atom
Helium He
Shell
Second most common element (atom) in
the Universe around 24% (nearly 1/4) of
all matter is helium.
Made in stars like our own sun by
“fusing” from hydrogen
The Amazing Atom
Atomic Symbols
Short name for this element
H = Hydrogen, He = Helium
4He
2
Mass number = no. of
protons and neutrons in
the nucleus
(sometimes shown)
Atomic number = no. of
protons in the nucleus
(often shown)
BUT MASS AND ATOMIC NUMBERS CAN BE
REPRESENTED IN DIFFERENT POSITIONS!
The Amazing Atom
Oxygen 168 O
Third most common element but tiny in
comparison – only about 1% (1/10)
The Amazing Atom
The flighty little electron
Electrons may be small but they are
powerful!
They play a big role in light, chemistry,
electricity and in magnetism
We shall come back to them time and
time again
The Amazing Atom
The flighty little electron
Electrons in outer incomplete shells can
interact with other atoms, leap to other
shells (quantum leap), or be stripped off
altogether and fly away!
The Amazing Atom
The electron orbits in shells
They find it very difficult to escape from
full shells – so atoms with complete outer
shells with the right number of electrons
in them, do not interact with other atoms
readily.
No. of electrons in shell = 2 x n x n = 2n2
where n = shell number from nucleus, no. 1, 2, 3, etc.
The Amazing Atom
So what does an atom really
look like?
Hydrogen atom
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