Tetrahedral in Molecular Geometry: Definition, Structure & Examples

Instructor: Mia Primas

Mia has taught math and science and has a Master's Degree in Secondary Teaching.

In this lesson, we'll learn what a tetrahedral is in molecular geometry. We'll also look at features and examples of tetrahedral structures. At the end of the lesson, take a brief quiz to see what you learned.

Molecular Geometry

When we think of the structures of molecules in chemistry, we usually think of them as 2-dimensional shapes. They are usually drawn this way for simplicity; however, many molecules have a 3-dimensional structure. Molecular geometry is a type of geometry used to describe the shape of a molecule. There are several shapes in molecular geometry, but in this lesson, we'll focus on the tetrahedral.

A tetrahedral has a central atom surrounded by four other atoms. The central atom bonds with each of the surrounding atoms, which form bond angles of 109.5 degrees.

Structure of a Tetrahedral Molecule

Valence Shell Electron Repulsion Theory

When identifying the shape of a molecule, we need to identify the number of bonds and lone electron pairs of the molecule. The lone electron pairs are the electrons that surround the central atom but are not bonded to another atom. The total number of bonds and lone electron pairs determine the steric number of the molecule. Tetrahedral molecules have a steric number of four because they have four bonds and no lone electron pairs.

The presence of lone electron pairs affects the shape of the molecule. According to the valence shell electron repulsion theory (VSEPR), electron pairs repel each other whether they are bonded or in lone pairs. This repulsion is due to the negative charge of the electrons, which means like charges repel each other. VSEPR theory also states that the electrons and atoms of the molecule will arrange themselves to minimize the repulsion, which gives the molecule its geometric structure.

Not all molecules with a central atom and four surrounding atoms are tetrahedral. A square planar molecule also has a central atom bonded to four surrounding atoms. However, it has two lone electron pairs, shown in red in the image below, giving it a steric number of six. The lone electron pairs arrange themselves so that they are opposite from each other. This pushes the other bonds closer together so that they are on the same plane arranged 90 degrees from each other. This arrangement does not occur with the tetrahedral because there are no lone electron pairs; instead, the bonds are spread evenly throughout the 3-dimensional space.

Comparison of a Tetrahedral Molecule and Square Planar Molecule

To unlock this lesson you must be a Study.com Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account