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Science Gizmo – Ions & Ionic Bonding
Name ___________________________
Computer (Number & Letter) __________
Period _________
Date Monday, 3 / 31 / 08
Student Exploration Guide: Ionic Bonds
Sodium is a soft, silvery metal that reacts violently with water and air. Chlorine is a poisonous gas
used to kill bacteria in swimming pools and drinking supplies. If ingested, each could cause a
quick and painful death. But together, sodium and chlorine form salt, a necessary nutrient for all
living things! How can these two dangerous substances combine to form a harmless crystalline
solid?
The answer lies in ionic bonds. Sodium is highly reactive because it has a single outer electron,
called a valence electron, that is easily lost. Chlorine, on the other hand, has a strong tendency
to gain an electron. When atoms gain or lose electrons, they become charged atoms called ions.
Ions with opposite charges are attracted to one another and form ionic bonds. When sodium and
chlorine form an ionic bond, the result is the stable, non-reactive substance we know as salt.
Forming Ionic Bonds
In this activity, you will discover how the electron arrangements of atoms determine their ability
to form bonds.
In the Gizmo™, observe the red sodium atom and blue chlorine atom in the SIMULATION pane.
Click Play, and observe the electrons orbiting the nucleus of each atom.
In the Gizmo, only the outermost electrons, or valence electrons, are shown.
1) How many valence electrons are visible on the sodium atom? _____________
2) How many valence electrons are visible on the chlorine atom? ______________
3) Sodium has a total of 11 electrons, and chlorine has a total of 17. How many electrons are
NOT shown on each atom? ___________ These electrons are found on the first two energy
levels. (The first level has _____________ electrons and the second has _____________.)
Some atoms give up electrons quite easily, and some do not. Try clicking and dragging an
electron away from each atom.
4) Which atom easily gives up its valence electron(s)? _______________ Atoms that easily lose
their valence electrons are called metals.
Drag the electron from the sodium atom to the chlorine atom. (If the electrons are moving too
fast, adjust the Speed slider or click Pause .)
The tendency of an atom to attract electrons is called electron affinity.
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5) Which atom has a greater electron affinity? (Na or Cl) _____________ Atoms that have a
strong electron affinity (and therefore tend to gain electrons) are called nonmetals. Metals
have a low electron affinity, which explains their tendency to lose valence electrons.
6) How many valence electrons does the sodium atom appear to have now? ____________
7) How many valence electrons does the chlorine atom have now? ______________
Atoms are most stable when their outermost energy level is full of electrons. The
third energy level of the sodium atom is now empty. Therefore, the second level is now the
outermost, with eight electrons.
8) Are both atoms currently in a stable configuration? _________
A normal sodium atom has eleven protons, each with a positive charge. It also has eleven
electrons, each negatively charged so that the atom is neutral.
9) After losing an electron, what do you think is the charge of the sodium atom? __________
10) Write down your hypothesis (why you think it has that charge).
_________________________________________________________________________
Before gaining an electron, the chlorine atom had 17 protons and 17 electrons.
11) What is the charge of the chlorine atom now? _____________ Write this down, then
check your hypotheses by clicking the Show charge checkbox. Were you correct?
_________ Charged atoms are called ions.
Ions with opposite charges are attracted to one another, forming an ionic bond. To represent
this bond, click on the nucleus of the sodium ion and drag it closer to the chlorine ion.
Click Check.
12) What is the name of the substance you created? ___________________________
Click Show formula.
13) What is the chemical formula of the substance you created? _________________
Click Show completed compounds. A list of formulas that you have completed correctly
will appear here.
Choose Lithium (Li) from the Select a metal menu and Oxygen (O) from the Select a
nonmetal menu. Count the number of valence electrons in each atom.
14) Li __________ & O ___________
Transfer the valence electron from the lithium atom to the oxygen atom.
15) How many valence electrons does the oxygen atom have now? _______________
16) Is the oxygen atom stable?____________ When you have finished, click Check.
The oxygen atom needs 8 valence electrons to reach stability. To provide an additional
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electron, click Add metal. When the new lithium atom appears, transfer the remaining
electron.
17) Is the oxygen atom stable now? _________ Why or why not? ________________________
18) What is the formula of lithium oxide? ______________________________
Click the Show charge checkbox. Notice that each lithium ion has a 1+ charge, while the
oxygen ion has a 2− charge.
18) What is the total overall charge of the three ions? __________________________________
Because the positive charges of each lithium atom repel one another, the lithium
atoms will be found on opposite sides of the oxygen atom.
Try several combinations of metals and nonmetals. Transfer electrons from the metal atoms to
the nonmetal atoms. If the metal atom has one or more electrons left over, click Add nonmetal
to add an additional nonmetal atom. If the nonmetal has additional spaces to fill, click Add
metal. Extra atoms can be dragged to the Trash icon and eliminated, or you can start over by
clicking Reset. Once all electrons have been transferred, rearrange the atoms to show the
attraction between positive ions and negative ions.
What is the formula when the metal has 2 valence electrons and the nonmetal has 7?
19) For example, what is the formula of magnesium fluoride? ______________________
What is the formula when the metal has 2 valence electrons and the nonmetal has 5?
20) For example, beryllium and nitrogen. ____________________________
Try the remaining combinations of metals and nonmetals. For each that you do, write down a
predicted formula based on the numbers of valence electrons. Then, use the Gizmo to check
your answer.
21) Prediction
Checked answer
___________________________
____________________________
___________________________
____________________________
Extension Activity: Chemical Families
In the periodic table, elements are grouped by their chemical properties. These groups, also
called families, are determined by the valence electrons. Obtain a periodic table. Each column
in the periodic table is a family of elements with similar properties.
In the Gizmo, select Lithium (Li) from the list of metals.
1) How many valence electrons does lithium have? _____________
2) According to the periodic table, what other element (from the Select a metal menu) is in
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the same chemical family? ___________________
3) How many valence electrons do you think this other element has? ______________
Use the Gizmo to check your answer.
4) How many valence electrons would you expect for potassium (K), rubidium (Rb), and cesium
(Cs)? ______________
5) Try finding other pairs of elements from the same family in the Gizmo. What patterns do you
see? ______________________________________________________________________
Notice that the elements in group 18 of the periodic table are not found in this Gizmo. These
elements are called noble gases and do not readily react to form compounds.
6) Based on the periodic table and what you have seen in the Gizmo, how many valence
electrons do most noble gases have? _____________
Why don't these gases form ionic bonds? __________________________________________
When Dmitri Mendeleev first published his periodic table in 1869, nothing was known about
valence electrons. Instead, Mendeleev used chemical properties to group elements together.
In the Gizmo, create a compound of lithium and oxygen.
7) What is the formula of lithium oxide? ___________________________
8) Create a compound of sodium and oxygen. What is the formula of sodium oxide? _________
9) How is this formula similar to lithium oxide? ______________________________________
10) Create a compound of beryllium and oxygen. What is the formula of beryllium oxide?
______________
11) Based on this formula, what do you think the formula of magnesium oxide will be? ________
Use the Gizmo to check your answer.
12) Create compound of aluminum and oxygen. What’s the formula of aluminum oxide? _______
13) What would you predict the formula of gallium oxide to be? ________________
14) Based on the patterns you observed, what is the formula of strontium bromide (Sr and Br)?
________________ Gallium phosphide (Ga and P)? ______________
Cesium telluride
(Cs and Te)? _________________
15) In general, what do elements from the same family have in common? __________________
__________________________________________________________________________
HOMEWORK – Finish the 5 Assessment Questions by the beginning of
tomorrow’s class if you don’t complete them during class.
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