Ions and Isotopes
Objective
Students will be able to:
•
•
use atomic symbols to represent
different atoms and their isotopes.
Identify and define ions of different
elements
Some definitions
• Ion - an atom that has a positive or
negative charge
How does something have a positive
or negative charge?
Number of protons and electrons
has to be different!
How can an atom become an ion?
• By gaining or losing electrons
Losing Electrons=
CATION
Gaining Electrons=
ANION
Cation
• Positive charge
• Formed by the atom losing electrons
A neutral atom of
sodium loses an
electron and
becomes Na+1
How many electrons does Li+1 have? Mg+2?
Anion
• Negative charge
• Formed by the atom gaining electrons
Chlorine gains
one electron
and becomes
Cl-1
How many electrons does Br-2 have? F-1??
Why do atoms become ions?
• Atoms want to have a full outer shell (orbital)
– one electron in outer shell will lose the electron.
– all but one electron will gain one.
Which is likely to become a cation?
Which is likely to become an anion?
Summary of Ions
Lose electrons- become positive, which is a cation
Gain electrons- become negative, which is an anion
Electrons are gained or lost in the outermost shell
• These are called valence electrons
Atomic Notation
m
a
Mass number=
protons + neutron
Atomic number=
Protons
40
20
Ca
P=
20
N=
20
E=
20
x
14
7
Element Symbol
N
P=
7
N=
7
E=
7
Atom Builder game
Isotopes
• Isotopes are atoms of the same element that
have different numbers of neutrons.
• The mass number of an isotope tells you the
number of protons plus the number of neutrons.
Difference?
Similarities?
H-1
H-2
H-3
http://web.visionlearning.com/custom/chemistry
/animations/CHE1.3-an-isotopes.shtml
Learning Check
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
6
6
14C
6
#p _______
_______
_______
#n _______
_______
_______
#e _______
_______
_______
Solution
12C
6
13C
6
14C
6
#p
6
6
6
#n
6
7
8
#e
6
6
6
Heavy Water
Application of isotope
• Duterium- 21H can bind with oxygen
• Only occurs 1 in every 3200 molecules
• Concentrated heavy water is used for
development of nuclear weapons
• Can be poisonous to plants and animals.
Cobalt-60
Application of isotope
• Has one extra neutron in the nucleus
– Radioactive and emits gamma radiation, which
can pass through materials easily
– Sterilizes medical equipment and kills harmful
bacteria