What is the Bond Angle in Ethene?

S6-SA4-0281

Grade Level:

Class 10

AI/ML, Physics, Biotechnology, Space Technology, Chemistry, Engineering, Medicine

Definition

What is it?

The bond angle in ethene refers to the specific angle formed between the two carbon atoms and a hydrogen atom (H-C-C angle) or between two hydrogen atoms and a carbon atom (H-C-H angle) within the ethene molecule. Ethene (C2H4) has a planar structure, and its carbon atoms are sp2 hybridized, leading to bond angles of approximately 120 degrees.

Simple Example

Quick Example

Imagine you're making a rangoli design. If you draw three lines coming out from a central point, trying to spread them out as much as possible evenly, you'd naturally make angles that are roughly 120 degrees apart. Ethene's atoms are arranged similarly around each carbon, pushing each other away to create these 120-degree angles for maximum stability.

Worked Example

Step-by-Step

Let's figure out the bond angle for the H-C-H and H-C-C bonds in ethene:
1. Identify the central atom: In ethene (C2H4), each carbon atom is a central atom, bonded to one other carbon and two hydrogen atoms.
---2. Determine the hybridization of the central carbon atom: Each carbon atom in ethene forms a double bond with the other carbon and two single bonds with hydrogen atoms. This means each carbon has three 'groups' (one double bond, two single bonds) around it, with no lone pairs.
---3. Recall VSEPR theory for three electron domains: When a central atom has three electron domains (like three bonds and no lone pairs), it adopts a trigonal planar geometry.
---4. Determine the ideal bond angle for trigonal planar geometry: In a trigonal planar arrangement, the electron domains are spaced as far apart as possible, leading to ideal bond angles of 120 degrees.
---5. Apply to ethene: Therefore, both the H-C-H bond angle and the H-C-C bond angle in ethene are approximately 120 degrees.
Answer: The bond angles in ethene are approximately 120 degrees.

Why It Matters

Understanding bond angles is crucial in Chemistry and Biotechnology, as it dictates a molecule's shape, which in turn affects how it reacts or interacts with other molecules. For instance, in Medicine, drug designers use bond angles to create medicines that fit perfectly into specific sites in our body, like a key in a lock. Engineers also consider molecular shapes when designing new materials.

Common Mistakes

MISTAKE: Assuming ethene has a tetrahedral shape and 109.5-degree bond angles, like methane. | CORRECTION: Ethene has a carbon-carbon double bond, leading to sp2 hybridization and a trigonal planar geometry around each carbon, resulting in 120-degree angles.

MISTAKE: Confusing the bond angle with the number of bonds. | CORRECTION: The bond angle is about the spatial arrangement of atoms, determined by hybridization and VSEPR theory, not just the count of bonds.

MISTAKE: Thinking that the H-C-H angle is different from the H-C-C angle in ethene. | CORRECTION: Due to the trigonal planar geometry around each carbon, both the H-C-H and H-C-C bond angles are approximately 120 degrees.

Practice Questions

Try It Yourself

QUESTION: What type of hybridization does each carbon atom in ethene undergo? | ANSWER: sp2 hybridization

QUESTION: If a molecule has a trigonal planar geometry around a central atom, what is the ideal bond angle? | ANSWER: 120 degrees

QUESTION: Explain why ethene has a planar structure, unlike ethane (C2H6) which is not planar. | ANSWER: Ethene has sp2 hybridized carbon atoms, which results in a trigonal planar geometry around each carbon, making the entire molecule flat. Ethane has sp3 hybridized carbons, leading to a tetrahedral geometry around each carbon, making it non-planar.

MCQ

Quick Quiz

What is the approximate H-C-H bond angle in an ethene molecule?

109.5 degrees

180 degrees

120 degrees

90 degrees

The Correct Answer Is:

Ethene has sp2 hybridized carbon atoms with a trigonal planar geometry around each carbon, which leads to bond angles of approximately 120 degrees. Options A, B, and D correspond to tetrahedral, linear, and square planar geometries, respectively.

Real World Connection

In the Real World

Ethene is a very important chemical in industries across India! It's used to ripen fruits like mangoes and bananas faster, especially after transport from farms. Understanding its 120-degree bond angles helps scientists in the chemical industry design better catalysts to produce plastics (like polyethylene, used in many everyday items from water pipes to grocery bags) from ethene efficiently. Its molecular shape is key to these processes.

Key Vocabulary

Key Terms

BOND ANGLE: The angle formed between two covalent bonds originating from the same atom | ETHENE: A hydrocarbon with the chemical formula C2H4, containing a carbon-carbon double bond | HYBRIDIZATION: The mixing of atomic orbitals to form new hybrid orbitals suitable for the pairing of electrons to form chemical bonds | TRIGONAL PLANAR: A molecular geometry where a central atom is bonded to three other atoms, and all four atoms lie in the same plane, with 120-degree angles between the bonds | VSEPR THEORY: Valence Shell Electron Pair Repulsion theory, which predicts the geometry of molecules based on minimizing repulsion between electron pairs

What's Next

What to Learn Next

Great job understanding ethene's bond angle! Next, you should explore the bond angles in ethyne (C2H2). This will help you see how different types of carbon-carbon bonds (single, double, triple) lead to vastly different molecular geometries and bond angles.