Back To Course

High School Geometry: Help and Review13 chapters | 162 lessons

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.

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.

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.

**Methane**, a common example of a tetrahedral, has a carbon atom surrounded by four hydrogen atoms. The **ammonium ion** has a central nitrogen atom surrounded by four hydrogen atoms. Here, we see an overall charge of +1, represented by the *+* sign next to the nitrogen atom. The charge of the molecule does not affect the steric number and therefore has no effect on the geometric shape.

Likewise, the negative charge of the oxygen atoms found in the **phosphate ion** does not affect its shape. It is interesting to note that, although the phosphate has a double bond with one of the oxygen atoms, its steric number is still four. Remember that the steric number includes the number of bonded atoms, not the number of bonds. Take a look at the image below to see the chemical arrangements of these ions.

In **molecular geometry**, the number of bonds and lone electron pairs determines the shape of a molecule. **Valence shell electron repulsion theory** (VSEPR) explains how these negatively charged electron pairs are repelled by each other, be they bonded to each other or found lone pairs. In a **tetrahedral molecule**, there is one central atom bonded to four surrounding atoms, with no lone electron pairs. The bonds form angles of 109.5 degrees.

Some examples of tetrahedral molecules include the **ammonium ion**, **methane ion** and **phosphate ion**. Central atoms that are bonded to four atoms that are not tetrahedral are known as **square planar molecules**.

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

Create your account

Are you a student or a teacher?

Already a member? Log In

BackDid you know… We have over 160 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

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.

You are viewing lesson
Lesson
19 in chapter 5 of the course:

Back To Course

High School Geometry: Help and Review13 chapters | 162 lessons

- Applications of Similar Triangles 6:23
- Triangle Congruence Postulates: SAS, ASA & SSS 6:15
- Congruence Proofs: Corresponding Parts of Congruent Triangles 5:19
- Converse of a Statement: Explanation and Example 5:09
- The AAS (Angle-Angle-Side) Theorem: Proof and Examples 6:31
- The HA (Hypotenuse Angle) Theorem: Proof, Explanation, & Examples 5:50
- The HL (Hypotenuse Leg) Theorem: Definition, Proof, & Examples 6:19
- Perpendicular Bisector Theorem: Proof and Example 6:41
- Angle Bisector Theorem: Proof and Example 6:12
- Congruency of Right Triangles: Definition of LA and LL Theorems 7:00
- Congruency of Isosceles Triangles: Proving the Theorem 4:51
- Angle of Depression: Definition & Formula 5:20
- Law of Syllogism in Geometry: Definition & Examples 6:38
- Midpoint Theorem: Definition & Application 4:23
- Perpendicular Bisector: Definition, Theorem & Equation 5:23
- Proof by Contradiction: Definition & Examples 6:07
- Pythagorean Identities in Trigonometry: Definition & Examples
- Square Matrix: Definition & Concept 4:41
- Tetrahedral in Molecular Geometry: Definition, Structure & Examples
- Ceva's Theorem: Applications & Examples
- Go to Triangles, Theorems and Proofs: Help and Review

- GRE Information Guide
- Computer Science 310: Current Trends in Computer Science & IT
- Earth Science 105: Introduction to Oceanography
- Computer Science 331: Cybersecurity Risk Analysis Management
- Computer Science 336: Network Forensics
- World Literature: Drama Since the 20th Century
- Visual Art Since the 18th Century
- World Literature: Drama Through the 19th Century
- Defamation, Libel & Slander
- Elements of Music Overview
- ILTS Prep Product Comparison
- CTEL Prep Product Comparison
- TASC Prep Product Comparison
- FSA Prep Product Comparison
- SHSAT Prep Product Comparison
- MEGA Test Accomodations
- Study.com Grant for Teachers

- Materials & Resources for an Early Childhood Classroom
- Obstructive Shock: Causes, Symptoms & Treatment
- Interpreting & Calculating Seasonal Indices
- Managing Classroom Behaviors of Young Children
- Taekwondo Lesson Plan
- Normalization & Invisibility of Privilege in the Workplace
- Practical Application: Reducing Job Stress Using Time Management
- Solving Equations Using the Least Common Multiple
- Quiz & Worksheet - Real-World Applications of Learning
- Quiz & Worksheet - Dante's Inferno 4th Level of Hell
- Quiz & Worksheet - Coaching Agreements
- Quiz & Worksheet - Third-Person Pronouns
- Quiz & Worksheet - Code of Ethics for Teaching
- Flashcards - Measurement & Experimental Design
- Flashcards - Stars & Celestial Bodies

- 10th Grade English: High School
- Math 102: College Mathematics
- Nursing 101: Fundamentals of Nursing
- Foundations of Education: Certificate Program
- Introduction to Counseling: Certificate Program
- Athletic Scholarship Basics
- TASC Writing Flashcards
- Quiz & Worksheet - History & Types of Terrorism
- Quiz & Worksheet - Financial Markets & Allocating Capital in Economic Systems
- Quiz & Worksheet - Wallace's Religion Categories
- Quiz & Worksheet - History of the U.S. Criminal Justice System
- Quiz & Worksheet - Key Components of Root System Growth

- Types of Defense Against a Criminal Charge
- The Magnificent Ambersons: Book Summary & Characters
- Free ACT Math Practice
- What Are SAT Test Dates and Locations?
- Oregon Science Standards for 5th Grade
- Utah Science Standards for 4th Grade
- Homeschool Laws by State
- Excelsior College BS in Business Degree Plan Using Study.com
- How Long is the LSAT?
- Study.com's Workforce College Accelerator for Employees
- Romeo and Juliet Act 2 Lesson Plan
- How to Ace an Internal Interview

- Tech and Engineering - Videos
- Tech and Engineering - Quizzes
- Tech and Engineering - Questions & Answers

Browse by subject