SNC1D7
Atoms, Elements
& Compounds
Standard Atomic Notation
Atoms are made up of sub atomic particles: ________________________________________
Particle
Symbol
Location
Mass
Charge
Electron
Proton
Neutron
To represent subatomic particles in an atom use Standard Atomic Notation
X
Z
A
X = Mass number
Z = Atomic number
A = Element symbol
ie)
The Mass Number _________________________________________________
The Atomic Number ____________________________________.This determines
what element an atom is. ie) an atom with 6 protons will always be Carbon
Atoms are neutral and ____________________________________. Each atom
has the same amount of protons and electrons.
We can determine the number of protons, neutrons and electrons.
How did you figure it out?
27
56Fe
Protons ______________
_________________________
Neutrons ____________
_________________________
Electrons ____________
_________________________
When an atom is NOT neutral, it is called an ion. Atoms can either gain or lose
electrons. Protons do not change.
23
+
11 Na
19 9 F
p________ N ________ E ________
p________ N ________ E ________
Complete the following table.
Hint: Use a periodic table to find the name and symbols of the element!
Name of
Element
Symbol
Atomic
Number
Mass
#
#
# Protons
Number
Electrons Neutrons
oxygen
Hg
2
122
19
54
83
Cr
Draw the Standard Notation for:
Nitrogen
Kr Cu
Ions & Isotopes
SNC1D7
Atoms, Elements
and Compounds
IONS
 An ion is ________________________________________________
 Atoms become charged by _____________ or _______________ electrons.
(Protons never move!!)
 Gain electrons  ___________ ion (_________). Has more electrons than
protons.
 Lost electrons  ___________ ion (_________). Has more protons than
electrons.
 The number of electrons an atom gains or loses indicates the charge.
Example
1.
24
12Mg
2+
2.
Atomic number = _________
Mass number = _________
Number protons = _________
Number electrons = _________
Number neutrons = _________
19 F 19
Atomic number = __________
Mass number = _________
Number protons = _________
Number electrons = _________
Number neutrons = _________
Try these:
Name of Element Symbol
oxygen
Atomic #
Mass #
# Protons
8
Al+3
# Neutrons
10
8
13
3
Br -1
# Electrons
7
2
45
ISOTOPES
 An isotope is ______________________________________________
 Isotopes have the same __________________, therefore the same number of
______________, but have have a different number of _____________.
Therefore isotopes have a different _____________________!
 Isotopes of an element have different _____________________________
__________________than their standard counterpart.
 “Light” isotopes have _____________________ (lower mass).
 “Heavy” isotopes have ____________________ (more mass).
Why is this important?
The atomic mass found on the periodic table is actually a “weighted average”
of all isotopes of that element.
Example
12 C
6
14
Atomic number = _________
Mass number = _________
Number protons = _________
Number electrons = _________
Number neutrons = _________
6C
Atomic number = _________
Mass number = _________
Number protons = _________
Number electrons = _________
Number neutrons = _________
Try these:
Name of Element Isotope
3
____
25
Mass #
# Protons
# Electrons
1H
____ U
12Mg
37
Atomic #
17Cl
240
92
# Neutrons
The Structure of Atoms
SNC1D7
Atoms, Elements
& Compounds
Atoms are made up of three types of particles: _______________________, ____________________
and _________________________.
Particle
Electric Charge
Mass (in Atomic Mass Units)
Location in the Atom
Bohr-Rutherford Diagrams (BR diagrams)
BR diagrams are a model that describes ____________________________. Consider the atom of
lithium. What does the BR diagram look like?
Step 1
Calculate the number of protons, neutrons and electrons.
Atomic number =
Atomic mass =
therefore the mass number is
Therefore
# protons =
# neutrons =
# electrons =
Step 2
Draw the nucleus as a circle, and inside indicate the number of protons (p=
of neutrons (n=
)
) and the number
Step 3
Draw the electrons in their orbits. Only a certain number of electrons can be held in each orbit.
• The first orbit can only hold __________ electrons
• The second and third orbit can only hold ________ electrons
• Although they exist, we will not draw elements with more than three orbits.
Extra Rules:
• You have to put electrons into the lowest orbits first.
• Put electrons in the second and third orbits one at a time until you get 4 electrons in the orbit,
and then start to pair them up.
Draw the Bohr-Rutherford Diagram for Lithium
A Shortcut: As you can probably see, for large elements the BR diagram would get very cumbersome.
We often use a shortened form of the BR diagram. You do not worry about pairing electrons or drawing
dots. Instead:
• draw the nucleus as usual
• put partial circles to the right, and write the number of electrons for each orbit on the
circles
For Lithium:
Try drawing both types of Bohr Rutherford diagrams for aluminum below.
Homework: Draw BR diagrams for elements 1,2,3,5,8,10,11,14,17. Try element 19!
Bohr-Rutherford Diagrams for the First 20 Elements on the Periodic Table
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20