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Physical Science
A study of chemistry and physics
-Understanding and Drawing Atoms
Ions and Isotopes
Why is the overall charge of an atom
neutral?

The atom has the same number of positive charges (protons) as negative
changes (electrons).
# protons = # electrons
# of positive charges = # of negative charges
NO CHARGE !

How do we know how many protons and electrons are in each atom?
Look at the periodic table!
Atomic Number
All atoms of the same element
have the same number of
protons in the nucleus
13
Al
26.981
Atomic number
Element symbol
AVERAGE Atomic Mass
Atomic Number
the number of protons in the nucleus of an atom.
 The
number of protons in the nucleus
determines what the element is.
 The
atomic number will never change.
 Since
the atom has no charge……we can tell
how many electrons the atom has by the
atomic number. It has to be the same!
Atomic Number
Element
# of protons
Atomic #
Carbon
6
6
Phosphorus
15
15
Gold
79
79
Mass Number and Atomic Mass
 Mass
Number = the sum of the protons
and neutrons in an atom’s nucleus.
 Atomic Mass = the average mass of all
isotopes of that element as they occur
in nature.
Drawing Atoms

Determine the # of protons


Determine the # of electrons


Look at the Atomic Number
F
Will be the same as the # of protons
Determine the # of neutrons

9
18.998
Mass number – atomic # = # of neutrons
(Round the atomic mass number to nearest whole number ,
18.998 rounds to 19)
19 – 9 = 10 neutrons

Determine the placement of electrons in the energy levels

Level 1- holds no more than 2

Level 2- holds no more than 8

Level 3- holds no more than 18
Mass Number
Mass number is the number of protons and
neutrons in the nucleus of an isotope:
Mass # = p+ + n0
p+
n0
e- Mass #
8
10
8
18
Arsenic - 75
33
42
33
75
Phosphorus - 31
15
16
15
31
Oxygen - 18
Chemical Symbols

First letter of element’s name
S

Sulfur, O Oxygen, N Nitrogen
First two letters of element’s name
 Ca

First and third of later letter of element’s name
 Mg

Calcium, Ne Neon, He Helium
Magnesium, Mn Manganese Cl Chlorine
First letter or letters of name in Latin
 Fe
Iron (ferrum), Pb Lead (plumbum)
Fluorine Atom

Protons = 9

Neutrons = 10

Electrons = 9

Level 1= 2

Level 2 = 7
Isotopes
Atoms
of the same element must
have the same number of protons
but can have a different number of
neutrons. These atoms are known
as isotopes.
Isotopes are atoms of the same element having
different masses, due to varying numbers of
neutrons.
Isotope
Protons Electrons
Neutrons
Hydrogen–1
(protium)
1
1
0
Hydrogen-2
(deuterium)
1
1
1
1
1
2
Hydrogen-3
(tritium)
Nucleus
Isotopes
Elements
occur in
nature as
mixtures of
isotopes.
Isotopes are
atoms of the
same element
that differ in
the number of
neutrons.
Atomic Mass

How heavy is an atom of oxygen?
 It depends, because there are different
kinds of oxygen atoms.
 We are more concerned with the average
atomic mass.
 This is based on the abundance
(percentage) of each variety of that
element in nature.

We don’t use grams for this mass because
the numbers would be too small.
To calculate the average:
Multiply
the atomic mass of
each isotope by it’s
abundance (expressed as a
decimal), then add the
results.
If
not told otherwise, the mass of the
isotope is expressed in atomic mass
units (amu)
Atomic Masses
Atomic mass is the average of all the
naturally occurring isotopes of that element.
Isotope
Symbol
Carbon-12
12C
Carbon-13
13C
Carbon-14
14C
Composition of
the nucleus
6 protons
6 neutrons
6 protons
7 neutrons
6 protons
8 neutrons
Carbon = 12.011
% in nature
98.89%
1.11%
<0.01%
Atomic Symbols

Show the name of the element, a hyphen, and the mass number in hyphen
notation
sodium-23

Show the mass number and atomic number in nuclear symbol form
mass number
23
11
atomic number
Na
Complete Symbols
 Contain
the symbol of the element,
the mass number and the atomic
number.
Mass
Superscript →
number
Subscript →
Atomic
number
X
Symbols

Find each of these:
a) number of protons
b) number of
neutrons
c) number of
electrons
d) Atomic number
e) Mass Number
80
35
Br
Symbols

If an element has an atomic
number of 34 and a mass
number of 78, what is the:
a) number of protons
b) number of neutrons
c) number of electrons
d) complete symbol
Symbols
 If an element has 91
protons and 140 neutrons
what is the
a) Atomic number
b) Mass number
c) number of electrons
d) complete symbol
Symbols
 If an element has 78
electrons and 117 neutrons
what is the
a) Atomic number
b) Mass number
c) number of protons
d) complete symbol
Isotopes?
Which of the following represent
isotopes of the same element? Which
element?
234
92
X
234
93
X
235
92
238
X
92
X
Learning Check – Counting
Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the
number of protons, neutrons, and electrons in each of these carbon atoms.
12C
13C
14C
6
6
6
#p+ _______
_______
_______
#no _______
_______
_______
#e- _______
_______
_______
Learning Check
An atom has 14 protons and 20 neutrons.
A. Its atomic number is
1) 14
2) 16
3) 34
B. Its mass number is
1) 14
2) 16
3) 34
C. The element is
1) Si
2) Ca
3) Se
D. Another isotope of this element is
1) 34X
16
2) 34X
14
3) 36X
14
Isotope lab

Beans = proton

Corn = neutron
Atoms vs Ions


Since the number of electrons = the number of
protons the overall charge of an atom is neutral.
If an atom should lose or gain an electron it is not
longer an atom but a charged particle called an ion.
 if atom loses an electron, a POSITIVE ion is
created
 If atom gains an electron, a NEGATIVE ion is
created
IONS




IONS are atoms or groups of atoms with a positive or negative
charge.
Taking away an electron from an atom gives a CATION with a
positive charge
Adding an electron to an atom gives an ANION with a negative
charge.
To tell the difference between an atom and an ion, look to see if
there is a charge in the superscript! Examples: Na+ Ca+2 I- O-2
Na
Ca
I
O
Forming Cations & Anions
A CATION forms
when an atom
loses one or more
electrons.
Mg --> Mg2+ + 2 e-
An ANION forms
when an atom
gains one or more
electrons
F + e- --> F-
PREDICTING ION CHARGES
In general
 metals
(Mg)
 nonmetals
lose electrons --->
(F)
cations
gain electrons --->
anions
Learning Check – Counting
State the number of protons, neutrons, and electrons in each of these ions.
39 K+
16O -2
41Ca +2
19
8
20
#p+ ______
______
_______
#no ______
______
_______
#e- ______
______
_______
One Last Learning Check
Write the nuclear symbol form for the following
atoms or ions:
A. 8 p+, 8 n, 10 e-
___________
B. 17p+, 20n, 17e-
___________
C. 47p+, 60 n, 46 e-
___________
The Atoms Family Album
In the center of Matterville there is a
place called the Nucleus Arcade where
two member of the Atoms Family like
to hang out. Perky Patty Proton, like
her sisters, is quite large with a huge
smile and eyes that sparkle (+). Patty
always has a positive personality.
The Atoms Family Album
Nerdy Nelda Neutron is large like Patty,
but she has a boring, flat personality
and her eyes have zero expression (0).
Her family is very apathetic and
neutral about every thing. Patty,
Nelda, and their sisters spend all of
their time at the arcade.
The Atoms Family Album
Around the Nucleus Arcade you will find a series
of roadways that are used by another member
of the Atoms family, Enraged Elliot Electron.
Elliot races madly around the Arcade on his
bright red chrome-plated Harley-Davidson.
He rides so fast that no one can be sure where
he is at any time. Elliott is much smaller than
Patty and Nelda and he is always angry
because these bigger relatives will not let him
in the Arcade. He has a frown on his face,
eyes that are squinted with anger, and has a
negative (-) attitude.
The Atoms Family Album
The first energy street can only hold _____ electron
brothers. The second energy street, called the
Energy Freeway, can only hold___ brothers. The
third energy street, called the Energy
Superhighway, can hold ____of the brothers.
The Atoms Family Album
The morale of Matterville is stable as long as
each negative Electron brother is balanced
out by one _______ proton sister. The
number of residents in Matterville depends
on the Proton and Neutron families.
Challenge: What would happen to the morale
of Matterville if one Elliott Electron was
kidnapped?
The Atoms Family Song
They’re tiny and they’re teeny,
Much smaller than a beany,
They never can be seeny,
The Atoms Family
Chorus:
They are so small (snap, snap)
They’re round like a ball (snap, snap)
They make up the air,
They’re everywhere,
Can’t see them at all. (snap, snap).
The Atoms Family Song
Protons with a positive charge,
Neutral neutrons rather large,
Negative electrons really are
The Atoms Family.
Chorus:
They are so small (snap, snap)
They’re round like a ball (snap, snap)
They make up the air,
They’re everywhere,
Can’t see them at all. (snap, snap).
The Atoms Family Song
Protons, neutrons are inside,
In the nucleus they abide,
While electrons race outside.
The Atoms Family.
Chorus:
They are so small (snap, snap)
They’re round like a ball (snap, snap)
They make up the air,
They’re everywhere,
Can’t see them at all. (snap, snap).
The Atoms Family Song
Together they make gases,
And liquids like molasses,
And all the solid masses,
The Atoms Family!
Chorus:
They are so small (snap, snap)
They’re round like a ball (snap, snap)
They make up the air,
They’re everywhere,
Can’t see them at all. (snap, snap).