Electronegativity

The title of the Project: Electronegativity

This virtual laboratory is intended for use in chemistry classes on the following topics:

  • 8th grade. Chapter IX . “Electronegativity. Covalent bond”.
  • 10th grade. Chapter III. “Electronegativity and bond polarity”.

Objectives:

  •  to experiment with and understand the concept of electronegativity.
  •  to observe how changes in electronegativity affect the polarity (dipole moment) of a bond between two atoms.
  •  to see how the polarity of a molecule influences its alignment in an electric field.

Practical part

This guide will walk you through using the PhET “Molecule Polarity” simulation to understand electronegativity in chemistry.

1.Launch the Simulation. Notice the three tabs: “Two Atoms”,  “Three Atoms” and “Real Molecules” (Java version required). We’ll focus on the “Two Atoms” model for now.

2.  Each atom has an “Electronegativity” slider. Checking the “Bond Dipole” box will show an arrow representing the bond polarity (dipole moment) if it exists. The size and direction of the arrow indicate the strength and direction of the polarity.Slide the “Electronegativity” bars back and forth to see how the electronegativity of each atom affects the molecule.

3.You can also choose to view “Partial Charges” and “Bond Character” by checking the boxes.  Partial charges show the slight positive or negative charge on each atom due to electronegativity differences. Bond character indicates the type of bond formed (ionic, covalent, etc.) based on electronegativity.

4. Explore by clicking the “Electron Density” button. This shows areas of high and low electron density.  Click “Electrostatic Potential” to see positive and negative charge regions within the molecule.

5. Click and drag the molecule to rotate it in any direction.  Then, click the “Electric Field” button. Observe how the molecule aligns itself with the electric field, with the positive end attracted to the negative side of the field and vice versa.

6. Discuss how changing the electronegativity of each atom affects the bond polarity (dipole moment) size and direction.

7.Now switch to the “Three Atoms” model. Here, you can adjust electronegativity, bond angles, and view both “Bond Dipoles” and the overall “Molecular Dipole”. Explain how the arrangement of atoms can influence the overall polarity of a molecule with more than two central atoms.

Conclusion

This virtual simulation provides a dynamic and interactive environment for students to explore the concept of electronegativity. By manipulating electronegativity and observing its impact on bond polarity, electron density, and interaction with electric fields, students can gain a deeper understanding of this fundamental chemical concept. The simulation offers various functionalities for both simple two-atom molecules and more complex three-atom structures, allowing for a gradual progression in learning.