CP Biology
Name ______KEY___________________________________
Date ________________Per_______
Activity: How Ions Are Formed
Objective: In this activity you will be building ions of biologically important elements.
Introduction:
You have learned that a molecule is a compound that is composed of atoms joined by covalent bonds. Covalent
bonds form when atoms share electrons. They are strong bonds that help to form many different compounds. Proteins,
the large organic molecules necessary for life, are held together by strong covalent bonds.
Another type of compound important in biological systems is the ionic compound. Ionic compounds differ from
molecular compounds because they are made of atoms called ions.
Ion-An atom that has either lost or gained one or more electrons in order to become stable:
a) When an atom loses electrons to become stable, it becomes an ion with a _positive___ charge.
b) When an atom gains electrons to become stable, it becomes an ion with a _negative___ charge.
Ionic compounds are made of positive and negative charged ions that have been attracted to each other. When
ions are mixed in water, they separate or dissociate from each other. The resulting ions are then available for use in
different body processes.
Several important ions in the human body:
Ion
Calcium
Iron
Use in the body:
Ca2+
Fe2+
Sodium Na+
Important in the formation of bones and in the clotting of blood.
Used to build hemoglobin, the molecule that carries oxygen in blood cells.
Found in and out of all cells in the body. Used in nerve cells.
Potassium K+
As above.
Cl-
As above.
Chloride
Magnesium Mg2+
An important compound that helps metabolic reactions take place.
What types of ions will be formed from the elements above? Will they form ions with a positive or negative
charge? How many electrons will they gain or lose?
Procedure:
Answer the following questions to determine what types of ions will be formed from the above compounds.
1) What charge does one proton have? _____+1________________________
2) What charge does one electron have? ____-1___________________________
3) How many protons does an atom of carbon have? ___6________ How many electrons? ____6________
4) Explain why atoms in their elemental form, like carbon above, do not have a charge and are neutral.
_________The 6 positive charges of the 6 protons balance out the 6 negative charges of the 6
electrons._____________________________________________________________________________________
Collect the following materials: paper clips to represent electrons
pennies to represent protons
chalk to draw the nucleus and energy levels
The Periodic Table of the Elements
Use the chalk to draw a small circle about the size of your hand in the center of your desk. This will represent the nucleus
of an atom. You will draw energy levels around the nucleus depending upon the number of electrons in the atom you are
asked to draw.
5) Build the atom called Fluorine:
a) What is the atomic number of Fluorine? __9_____ How many protons does Fluorine have? _____9_____
Place this number of pennies inside the nucleus you have drawn
b) How many electrons does Fluorine have? ____9__________
Count this number of paper clips to represent electrons.
c) How many electrons will be in the first energy level of Fluorine? ______2_________
Draw a circle around the nucleus to represent the first energy level.
Place paper clips representing the correct number of electrons on the circle.
d) How many electrons will be in the second energy level of Fluorine? ___7__________
Draw a circle around the nucleus to represent the second energy level.
Place paper clips representing the correct number of electrons on the circle.
e) Will there be electrons in the third energy level? _____no__________
6) Look at the atom of Fluorine that you have created. Is it stable and non-reactive or is it unstable and reactive?
How do you know? _____It has one vacancy in the valence shell__________
______________________________________________________________________________________________
7) In order to become stable would it be easier for Fluorine to lose 8 electrons or gain one electron? ______________
(Keep in mind that it is difficult to move larger numbers of electrons.)
8) Add or remove the correct number of paperclips (electrons) to make a stable Fluorine ion.
9) Now, count the number of pennies and paperclips in the Fluorine ion.
Number of pennies (protons) ____9____Number of paperclips (electrons) ___10________
10) Do you have more protons or electrons? ________________ How many more? _____1_________
11) How many positively charged particles are in the Fluorine ion? __9_________ Negative particles? ___10________
12) What is the charge of the Fluorine ion? (positive, negative) _______________________________
13) We write the chemical formula for Fluorine as F-. This shows that the ion carries one more electron than protons. If
an ion has two more electrons, it is written with a superscript of
2-
. Three electrons in an ion are shown with 3-.
14) Ions can also lose electrons to become stable. An ion with one more proton than electrons is written with a
superscript of ___1+__________. An ion with two more protons is written with a superscript of __2+_______.
Calcium forms a positive ion written as Ca2+.
15) Repeat the above exercise for each of the following atoms and fill in the chart.
Atom
H
Mg
Cl
Na
# protons
1
12
17
11
# electrons
1
12
17
11
# e in outer energy level
1
2
7
1
will atom lose or gain an electron to
Lose 1
Lose 2
Gain 1
Lose 1
1
12
17
11
remaining electron(s) (paperclips)
0
10
18
10
final charge of ion
1+
2+
1-
1+
chemical formula for ion
H1+
Mg2+
Cl1-
Na1+
become stable? How many?
remaining proton(s) (pennies) in
the ion
Note: Hydrogen is composed of only one proton and one electron. Its electron is easily pulled away by an atom like oxygen.
Hydrogen usually forms a positive ion called a hydrogen ion (H +) or, more simply, a proton.
Ionic Bonding
An ionic bond is formed when one or more electrons are transferred from one atom to another. The oppositely charged ions
have a strong attraction, forming an ionic bond. Water easily dissolves ionic compounds.
These two ions are now attracted to
each other…that’s an ionic bond!