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The number of protons in the
nucleus is what makes the element
what it is.
If there are 6 protons, then it is
carbon.
Your pencil “lead” is graphite, which
is actually Carbon.
If the atom has just one more
proton, then it would be Nitrogen
(78% of every breath you breath is
Nitrogen).
The difference between being a dark solid that
you can write on your paper with, or a colorless,
odorless gas that you breath is just one proton.
But when it comes to reacting
with other elements, it is the
electrons that do all the
work.
Of course the electrons would
not be with the atom if it
weren’t for the positive
charge of the protons
keeping them there.
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For each proton that an element has in a neutral atom there is
one electron. It is almost as if they were a matched pair that
comes to a couples only dance party.
Each electron must fit into an electron cloud around the
nucleus, but there are only certain places that they can be.
They always fill in a spot closest to the nucleus. Each shell
can only hold so many electrons before it is full. This is
similar to cars parking in a multi- level parking deck next to a
restaurant. Everyone wants to park as close to the
restaurant as possible.
8 Cars can fit
8 Cars can fit
Parking Deck
8 Cars can fit
2 Cars can fit
Restaurant
The Bohr Model shows all of the electrons of an
element in circular rings. Each ring represents an
electron shell.
It’s actually more
complicated than
this, but this is close
1st shell can hold 2
enough for 8th grade
science
2nd shell can hold 8
3rd shell can hold 8
4th shell can hold 8
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atomic number = # of protons
for a neutral atom, # of protons = # of electrons
atomic mass rounded to the nearest whole
number is the mass number of the most
common variety of the element
Niels Bohr
mass number - # of protons = # of neutrons
So we need a 1+ in the middle to show Hydrogen’s 1 proton.
We only have to put one electron.
1.008 rounds to 1, and 1-1=0 so there are no neutrons.
1+
0n
6 protons (also means 6 electrons have to be there)
12.011 rounds to 12 (#p+ + #n0)
subtract the 6 protons
12 – 6 = 6 (so it also has 6 neutrons)
6 protons
6 neutrons
6 electrons
6+
6n
Remember to follow the parking lot rules.
Always start on the inner most ring and work outward.
18 protons (also means 6 electrons have to be there)
39.948 rounds to 40 (#p+ + #n0)
subtract the 18 protons
40 – 18 = 22 (so it also has 22 neutrons)
18 protons
22 neutrons
18 electrons
18+
22n
Remember to follow the parking lot rules.
Always start on the inner most ring and work outward.
19 protons (also means 6 electrons have to be there)
39.098 rounds to 39 (#p+ + #n0)
subtract the 19 protons
39 – 19 = 20 (so it also has 20 neutrons)
19 protons
20 neutrons
19 electrons
19+
20n
Remember to follow the parking lot rules.
Always start on the inner most ring and work outward.
No matter how many layers the candy has,
your tongue can only taste the outer most
layer. The electrons of an atom are similar.
Only the atoms on the outer most layer can
interact with other elements.
The outer most electrons
are called the valence
electrons. Since the Bohr
model can get very difficult
to read for larger elements,
there is a way to show the
element with just the
valence electrons. It is the
Lewis Dot Diagram.
In the Lewis Dot Diagram we show the atomic
symbol surrounded by dots that represent the
valence electrons. Only these outer most
electrons are represented. Generally speaking we
start on the top and go around clockwise and only
put dots on top, sides, and bottom.
Gilbert N. Lewis
www.123rf.com
1+
0n
6+
6n
18+
22n
19+
20n
The Lewis Dot Diagram only shows the outer most electrons (valence electrons) surrounding the atomic symbol.