Bohr-Rutherford Diagrams: show the numbers and
locations of protons, neutrons and electrons in an
atom
 e.g.
the Bohr-Rutherford diagram of
Phosphorus (P)
p=
n=

All the information you need comes from the Periodic
Table of Elements!
Recall:
Atomic Number
Atomic mass
=
=
# of protons
= # of electrons
+ # of neutrons
# of protons
(*round to get mass number)
atomic number
6
C
atomic mass (*round to 12
for mass number)
12.01


Step 1: Draw the nucleus as a solid circle.
Step 2: Put the number of protons (atomic number) and the
number of neutrons inside the nucleus.
p = __
n = __

Step 3: Draw the correct number of orbits by drawing circles
around the nucleus.
p=
n=
1st orbit
2nd orbit

Step 4: Place the correct number of electrons (same number
as protons) in the orbits represented by a solid dot.
p=
n=
1 electron

Electrons are found in distinct orbits (or shells)


Each orbit represents an energy level
Electrons are NEVER found in between orbits—they are either in one
orbit or another orbit



NOTE: they can “jump” to and from different orbits IF they gain or lose energy
Each orbit holds only a specific number of electrons:
Orbit
Number of Electrons
1
2
2
8
3
8
4
8
Once ONE orbit is full, electrons begin filling the NEXT orbit

Do NOT start filling the next orbit until the previous one is filled!

Draw the Bohr-Rutherford diagram for Beryllium

Draw the Bohr-Rutherford diagram for Aluminum
 The
chemical reactivity of each of the
families of elements can be explained by
looking at just the outer shell (the last or
outermost orbit) of electrons called the
valence electrons

e.g Phosphorus has
5 valence electrons
outer
shell

You can also determine the number of valence
electrons by looking at which group (or family)
the element is in:

Group 1 elements: have 1 valence electron

Group 2 elements: have 2 valence electrons

Group 17 elements: have 7 valence electrons

Group 18 elements: have 8 valence electrons
18
18
1
1
2
3
4
5
6
7
2
13 14
15
16 17
 How
many valence electrons does Calcium have?
that all of the noble gases have
their outermost shells completely filled
 Notice
 This
is what makes them non-reactive
(or stable)
 When
an atom has ALL 8 electrons in
the outermost shell, it is often called a
stable octet
 All
elements other than the noble gases
attempt to have full outer shells so that they
can be stable too (stable = HAPPY )

gain 1 eto be full
For example:


Halogens would be stable IF they
could gain an extra electron
Alkali metals would be stable IF they
could lose one electron
F
lose
1 eto be
full
Na
 You
can also determine the number of
orbits/energy levels each element has by
looking to see what period it is in:

Period 1 elements: have 1 orbit

Period 2 elements: have 2 orbits

Period 3 elements: have 3 orbits

Period 4 elements: have 4 orbits
18
1
1
2
3
4
5
6
7
2
13
14
15
16 17
 How
many orbits does Nitrogen contain?
 When
an atom is not neutral, it is considered
to be an ion
 An
ion forms when an atom loses or gains one
or more electrons (without changing its
number of protons)
Ion: a particle that has either a positive or a
negative charge
 If
an atom loses an electron, it has one more
proton than electrons, and therefore has a net
POSITIVE CHARGE

Cation: a positively charged ion
 If
an atom gains an electron, it has one more
electron than protons, and therefore has a net
NEGATIVE CHARGE

Anion: a negatively charged ion
 We
represent ions by writing the element
symbol, then adding a superscript to indicate
the charge
 Examples:
Na+
 Cl O2 Mg2+

(this
(this
(this
(this
means
means
means
means
Na lost 1 electron)
Cl gained 1 electron)
O gained 2 electron)
Mg lost 2 electrons)
 Bohr-Rutherford
diagrams of ions are almost the
same as those of neutral atoms, however…

Because the atom has gained or lost electrons to
become stable, all orbits will be filled! (stable octets)

A square bracket is added around the diagram and the
charge is added at the top right corner outside the
bracket
+
11p+
12n0
11p+
12n0
Draw the Bohr-Rutherford diagram of O2- :
Draw the Bohr-Rutherford diagram of Ca2+ :
Homework:
 Read pg. 236 - 239 in textbook and do
Q: #7 – 8 on pg. 240
 Complete both sides of worksheet: “BohrRutherford Diagrams (The First 20 Elements”
and “Patterns in the Periodic Table”