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Lesson 5:
Bohr Diagram
Atoms and Ions
Ions: charged particles (atoms) that have lost or gained
electrons. They lose or gain electrons in order to have an
electron structure similar to that of a Noble gas.
Reason: Noble gases are stable!!
Comparing atoms to ions.
Atoms
Ions
- neutral charge
- # of electrons equal
atomic number
- positive or negative charge
- # of electrons is different
from the atomic number
- protons equal atomic
number
- protons equal atomic
number
• The atomic mass is the same for both ions and atoms because
electrons have such a small mass that they can be ignored.
Draw a Bohr diagram.
To draw Bohr Diagrams:
1. Draw the nucleus as a solid circle.
2. Put the number of protons (atomic number) in the
nucleus with the number of neutrons.
3. Place the number of electrons in orbits around the nucleus
by drawing circles around the nucleus.
1st shell – 2 e-, 2nd shell – 8 e-, 3rd shell – 8 e-, 4th shell – 18 eFor oxygen.
16
8
O
8 p+
8 n0
For sodium.
22.99
Na
11
11 p+
12 n0
Your turn: draw these diagrams for the first twenty
elements.
METALS:
-tend to lose electrons.
-become positively charged.
-the size of the positive charge is determined by the number of
electrons lost.
-the number of electrons lost is determined by the proximity to the
nearest Noble gas.
-named by using the full metals name and adding ion at the end.
eg:
Magnesium is a group two element.
12 electrons.
An atom of magnesium has ____
10 electrons.
neon and it has ______
The nearest Noble gas is ________
An ion of magnesium must also have _______
electrons
10
because this is a more stable configuration. This results in
magnesium having a net charge of 2+. It is named
___________________
magnesium ion
NON-METALS:
-tend to gain electrons.
-become negatively charged.
-the size of the negative charge is determined by the number of
electrons gained.
-the number of electrons gained is determined by the proximity of
Noble gas.
-named by dropping the ending and adding an ‘ide’ ending
Eg:
Chlorine.
17 electrons.
An atom of chlorine has _______
18
argon and it has ______
The nearest Noble gas is ________
electrons.
18
An ion of chlorine must also have _______
electrons because
it is more stable. This results in chlorine having a net charge of
1-. The name is __________
chloride
Valence Electrons
Elements in the same family have the same
number of outermost electron.
These electrons are called valence electrons.
Valence electrons are responsible for chemical
reactions.
Try this:
1. How many electrons does Al atom
possess?
13
2. How many valence electrons does Al
atom possess?
3
Octet Rule
States that atoms bond in such a way as to
have eight electrons in their valance
energy level.
Atoms try to bond to become stable like
the noble gasses. They will lose or gain
electron in order to have eight in their last
energy orbital.
Look back at the Aluminum Atom
It has 3 valence electrons.
If it wants to become stable, it
has to lose 3 electrons and
it will have the same number
of electrons as Neon.
That is why Aluminum ion
is
Al
3+
Check This Out
There is a pattern in the periodic table for
the charges.
Try this: What is the ionic charge for:
Alkali
Alkaline Earth Metals
Halogens
Noble Gasses
+1
_______
+2
_______
_______
-1
_______
0
Homework:
1. Finish drawing Bohr Diagram for the
first 20 elements.
2. Read pg 35, 38 and complete
questions 3, 5, 6, 9, 10, 12