Student Exploration: Ionic Bonds

Vocabulary: chemical family, electron affinity, ion, ionic bond, metal, nonmetal, octet rule, shell, valence electron

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

1.   Nate and Clara are drawing pictures with markers. There are 8 markers in a set. Nate has 9

markers and Clara has 7. What can Nate and Clara do so that each of them has a full set?

2.   Maggie is sitting at a table with Fred and Florence. Maggie has 10 markers, but Fred and

Florence each have only 7 markers. How can they share markers so each has 8?

Gizmo Warm-up

Just like students sharing markers, atoms sometimes share or swap electrons. By doing this, atoms form bonds. The Ionic Bonds Gizmo allows you to explore how ionic bonds form.

To begin, check that Sodium (Na) and Chlorine (Cl) are  selected from the menus at right. Click Play () to see electrons orbiting the nucleus of each atom. (Note: These atom models are simplified and not meant to be realistic.)

1.   Each atom consists of a central nucleus and several shells that contain electrons. The outermost electrons are called valence electrons.

How many valence electrons does each atom have?      Sodium: ______     Chlorine: ______

2.   Click Pause (). Elements can be classified as metals and nonmetals. Metals do not hold on to their valence electrons very tightly, while nonmetals hold their electrons tightly.

Electron affinity is a measure of how tightly the valence electrons are held.

A.  Try pulling a valence electron away from each atom. Based on this experiment,

which atom is a metal? ______________   Which is a nonmetal? _______________

B.  Try moving an electron from the metal to the nonmetal. What happens? __________

Introduction: Some of the particles that make up atoms have an electrical charge. Electrons are negatively charged, while protons are positively charged. Particles with opposite charges (+ and -) attract, while particles with the same charge (+ and + or - and -) repel.

Question: What happens when atoms gain or lose electrons?

1. Count: Electrons move around the nucleus of atoms in specific shells, shown by the rings around the atoms in the Gizmo. The first ring holds two electrons, and the second holds   eight. (If you like, you can hide the inner electrons by selecting Hide inner electrons.)

A.  Observe the sodium and chlorine atoms. How many electrons are there total in each atom?

Sodium: ____________________    Chlorine: ___________________

B.  Each atom is neutrally charged, which means that each atom has the same number

of protons and electrons. Based on this, how many protons are in each atom?

Sodium: ____________________    Chlorine: ___________________

2. Observe: Most atoms are stable with a configuration of eight valence electrons. This is

known as the octet rule. How many valence electrons does each atom have?

Sodium: ____________________    Chlorine: ___________________

3. Form. a bond: Each electron has a charge of 1-, and each proton has a charge of 1+. You

can calculate the charge of an atom by subtracting the number of electrons from the number of protons. Move an electron from the sodium to the chlorine atom.

A.  What are the charges of each atom now?      Sodium: _____     Chlorine: _____

Turn on Show charge to check. These charged atoms are called ions.

B.  Is each ion stable? Explain. ___________________________________________

Click Check in the lower right corner of the Gizmo to check.

4. Think and discuss: Why is there an attraction between the two ions in this chemical bond?

Question: How are ionic compounds formed?

1. Observe: Look at the purple lithium atom and the red oxygen atom. Recall that most atoms are stable when their outermost ring has eight electrons. Some atoms, such as lithium and beryllium, are stable when their outermost ring has two electrons.

A.  How many electrons will the lithium atom give up to become stable? _____________

B.  How many electrons does the oxygen atom need to become stable? ____________

C.  Can a stable compound be made from these two atoms? Explain why or why not.

___________________________________________________________________

2. Form. bonds: Click Add metal to add another lithium atom, and then transfer electrons from the lithium to the oxygen. Click Check.

A.  Did you make a stable compound? _______

B.  Turn on Show formula. What is the formula of this compound? ________________

C.  Turn on Show charge. What is the charge of each ion? Li _____  Li _____  O _____

3. Practice: Use the Gizmo to create stable compounds from the combinations given below.

After transferring electrons, arrange the atoms to demonstrate the attraction between positively charged ions and negatively charged ions. Click Check to check each compound.

For each compound, click the camera () icon to take a snapshot. Right-click the image, and click Copy Image. Paste each image into a blank document to turn in with this worksheet. Write the ionic charges (such as Ca2+) and chemical formulas below.

Ionic charges Chemical formula

A.  Lithium and fluorine:                     Li __    F __                            _________________

B.  Beryllium and oxygen:                  Be __  O __                            _________________

C.  Magnesium and fluorine:              Mg __  F __                            _________________

D.  Aluminum and chlorine:                Al __   Cl __                           _________________

E.  Beryllium and nitrogen:                Be __   N __                            _________________

Introduction: The periodic table arranges elements by size and property. The vertical columns represent chemical families, or groups of elements with similar chemical properties.

Question: How are elements arranged into chemical families?

1. Observe: Drag the nonmetal into the trash () so there is only the one lithium atom visible.

A.  How many valence electrons does lithium have? ______

B.  Now look at your periodic table. Find lithium (Li) in the first column. Other than

lithium, which element from the Gizmo is also in this column? __________________

C.  Choose this element. How many valence electrons does this element have? ______

2. Gather data: Four other pairs of elements in the same chemical family are listed below. List

the number of valence electrons in each element.

Beryllium _____ Nitrogen _____ Oxygen _____ Fluorine _____

Magnesium _____ Phosphorus _____ Sulfur _____ Chlorine ____

3. Analyze: What pattern do you see? _____________________________________________

4. Make a rule: Based on your data, how are elements arranged into chemical families?

5. Infer: Look at your periodic table. How many valence electrons would you find for elements  in each family?        Boron family: _____        Carbon family: _____        Neon family: _____

6. Think and discuss: How do you think the number of valence electrons relates to an

element’s chemical properties? ________________________________________________