Question

Given the following electronegativities $$ \mathrm{C}=2.5 \quad \mathrm{~N}=3.0 \quad \mathrm{~S}=2.6 $$ what is the central atom in CNS \(^{-}\) ?

Short answer

Answer: Carbon (C) is the central atom in the CNS- molecule.

Step-by-step solution

Identify the atom with the lowest electronegativity

To identify which atom has the lowest electronegativity, compare the given electronegativities: $$ \mathrm{C}=2.5 \quad \mathrm{~N}=3.0 \quad \mathrm{~S}=2.6 $$ The atom with the lowest electronegativity value is Carbon (C) with a value of 2.5.

Determine the central atom

Since Carbon has the lowest electronegativity value, it will be placed at the center of the molecule. Therefore, Carbon (C) is the central atom in the CNS\(^{-}\) molecule.

Key concepts

Central Atom Determination

When determining the central atom in a molecule, it's essential to consider certain factors. One significant factor is the electronegativity of the atoms involved. Electronegativity is a measure of how strongly an atom attracts electrons in a bond. Typically, the atom with the lowest electronegativity is selected as the central atom.
Certain rules can apply while selecting the central atom:

• The atom with the lowest electronegativity is often placed at the center. This is because it is less likely to hold onto its electrons tightly and can share them with surrounding atoms.
• Hydrogen is rarely the central atom since it can form only one bond.

The question asks us to identify the central atom in the ion CNS^{-}. Given the electronegativity values for C, N, and S, we see that Carbon, with the lowest electronegativity of 2.5, becomes the central atom.
By ensuring you correctly identify the atom with lower electronegativity for the central position, you establish a strong foundation for understanding the molecular structure.

Chemical Bonding

Chemical bonding involves the attraction between atoms that allows the formation of chemical substances containing two or more atoms. In the context of CNS^{-}, let's see how bonding occurs around the central atom, Carbon.
There are primary types of bonding to consider:

• Covalent Bonds: Atoms share electrons to achieve a full outer shell. For CNS^{-}, expect covalent bonds as Carbon shares electrons with Nitrogen and Sulfur.
• Polar and Non-Polar Bonds: Due to differences in electronegativity, polar covalent bonds have unequally shared electrons.
  • Nitrogen and Sulfur have higher electronegativities than Carbon, potentially creating polar bonds showcasing dipoles where electrons are unevenly shared.

Understanding the type of bond formed is crucial to predicting the behavior and properties of the molecule.

Molecular Structure

The molecular structure describes how atoms are arranged and bonded together. With CNS^{-}, the structure is established by arranging the atoms around the central Carbon atom.
The arrangement creates distinct features:

• Possible Linear Structure: Given Carbon's position and the types of bonds formed, CNS^{-} might exhibit a linear arrangement.
• Bond Angles: Determined by the bonding interactions surrounding the carbon atom. In simpler, linear formations, these angles are typically around 180°.
• Lone Pairs: Electron pairs not involved in bonding can affect the molecule's shape. However, for CNS^{-}, this factor depends on additional information about these atoms' electron configurations.

Understanding the molecular structure aids in visualizing and predicting the chemical behavior, reactivity, and interactions with other molecules.