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Mobile App Chapter 19: Problem 67
Write the Lewis structure for ethyne, \(\mathrm{C}_{2} \mathrm{H}_{2}\), and tell the bond angles.
Short Answer
Expert verified
The Lewis structure of \(\text{C}_{2}\text{H}_{2}\) includes a triple bond between the carbons. Bond angles are 180°.
Step by step solution
01
Count Total Valence Electrons
Determine the total number of valence electrons for \(\text{C}_{2}\text{H}_{2}\). Carbon (C) has 4 valence electrons each and hydrogen (H) has 1 valence electron. Thus, \(\text{C}_{2}\text{H}_{2}\) has \((2 \times 4) + (2 \times 1) = 10 \) valence electrons in total.
02
Arrange the Atoms
Arrange the carbon atoms in a linear structure with the hydrogens on either end: H–C–C–H. Each carbon needs 4 valence electrons to complete its octet, while each hydrogen needs 2 electrons.
03
Distribute Electrons to Form Bonds
Place one pair of electrons (representing a single bond) between each pair of bonded atoms: H:C:C:H. This accounts for 4 electrons (2 single bonds to hydrogen and 2 single bonds between the carbons).
04
Complete Octets by Forming Triple Bond
After placing the initially bonded pairs, 6 electrons remain. Place the remaining electrons to form triple bonds between the carbon atoms: H–C≡C–H. Each carbon in this configuration will now have an octet.
05
Verify the Electron Count
Check the total number of electrons used: there are 2 electrons in each hydrogen–carbon bond and 6 electrons in the carbon–carbon triple bond (2 + 2 + 6 = 10 electrons).
06
Determine the Bond Angles
Geometry around each carbon is linear because of the triple bond. The bond angle around each \(\text{C}\) atom is 180°.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Valence Electrons
Valence electrons are the outermost electrons in an atom and are crucial in forming bonds with other atoms. In the case of ethyne, also known as acetylene, we need to count the valence electrons to draw its Lewis structure.
Carbon (C) has 4 valence electrons, and hydrogen (H) has 1 valence electron. Therefore, for \(\text{C}_{2}\text{H}_{2}\), we have a total of \(2 \times 4 + 2 \times 1 = 10 \) valence electrons.
This counting is important as it determines how the atoms will bond and share electrons to form a stable molecule.
Carbon (C) has 4 valence electrons, and hydrogen (H) has 1 valence electron. Therefore, for \(\text{C}_{2}\text{H}_{2}\), we have a total of \(2 \times 4 + 2 \times 1 = 10 \) valence electrons.
This counting is important as it determines how the atoms will bond and share electrons to form a stable molecule.
Bond Angles
Bond angles are the angles between adjacent bonds in a molecule. For ethyne, because of its linear structure, the bond angles around each carbon atom are 180°.
This linear arrangement is due to the triple bond between the carbon atoms, which forces the surrounding bonds to spread out as far as possible.
Understanding bond angles is crucial for predicting the shape and reactivity of the molecule.
This linear arrangement is due to the triple bond between the carbon atoms, which forces the surrounding bonds to spread out as far as possible.
Understanding bond angles is crucial for predicting the shape and reactivity of the molecule.
Carbon Compounds
Carbon is unique in its ability to form long chains and rings, making it a fundamental element in organic chemistry. In ethyne (\(\text{C}_{2}\text{H}_{2}\)), each carbon forms three bonds with one another, resulting in a triple bond, and a single bond with hydrogen.
This ability to form multiple bonds (single, double, triple) allows carbon to create a diversity of compounds.
Learning about carbon compounds helps us understand everything from simple molecules like methane (\(\text{CH}_4\)) to complex macromolecules like DNA.
This ability to form multiple bonds (single, double, triple) allows carbon to create a diversity of compounds.
Learning about carbon compounds helps us understand everything from simple molecules like methane (\(\text{CH}_4\)) to complex macromolecules like DNA.
Linear Geometry
Linear geometry describes the spatial arrangement of atoms in a molecule where the bond angles are 180°. In ethyne, the carbon atoms and the hydrogen atoms are arranged in a straight line: H–C≡C–H.
The triple bond between the carbon atoms imposes this linear geometry, as it keeps the electron pairs as far apart as possible.
This geometric arrangement is essential to determining the physical and chemical properties of the molecule.
The triple bond between the carbon atoms imposes this linear geometry, as it keeps the electron pairs as far apart as possible.
This geometric arrangement is essential to determining the physical and chemical properties of the molecule.
Octet Rule
The octet rule is a principle stating that atoms tend to form bonds until they have a total of eight electrons in their valence shell, achieving a stable electron configuration similar to noble gases. In the case of ethyne, each carbon atom seeks to complete its octet.
Hydrogens only need two electrons (a duet) to achieve stability. In ethyne, each hydrogen forms a single bond with a carbon, and the carbon atoms themselves share three pairs of electrons (a triple bond), helping them both satisfy the octet rule.
Knowing the octet rule helps us predict molecular structure and bonding patterns.
Hydrogens only need two electrons (a duet) to achieve stability. In ethyne, each hydrogen forms a single bond with a carbon, and the carbon atoms themselves share three pairs of electrons (a triple bond), helping them both satisfy the octet rule.
Knowing the octet rule helps us predict molecular structure and bonding patterns.
