What is the oxidation number of carbon in CCl4?
The correct answer and explanation is :
Answer:
The oxidation number of carbon in CCl₄ is +4.
Explanation (around 300 words):
To find the oxidation number of carbon in carbon tetrachloride (CCl₄), we use the general rules for assigning oxidation numbers:
- The oxidation number of an element in its pure form is 0.
- The oxidation number of a monatomic ion equals its charge.
- Fluorine always has an oxidation number of -1; other halogens (like chlorine) usually have an oxidation number of -1 unless they are bonded to oxygen or fluorine.
- The sum of the oxidation numbers for all atoms in a neutral molecule must be zero.
Now, let’s apply these rules to CCl₄:
- CCl₄ is a neutral molecule, so the sum of all oxidation numbers must be zero.
- Each chlorine (Cl) atom is more electronegative than carbon and typically has an oxidation number of -1.
- There are four chlorine atoms, so the total oxidation number contributed by chlorine is:
4 × (-1) = -4.
Let x be the oxidation number of carbon (C). Setting up the equation:
[
x + (-4) = 0
]
[
x = +4
]
Thus, the oxidation number of carbon in CCl₄ is +4.
Why is this important?
Understanding oxidation numbers is critical in chemistry because it helps explain how electrons are transferred in chemical reactions, especially in redox (reduction-oxidation) reactions. Even though CCl₄ is a covalent compound (sharing electrons rather than transferring them completely like in ionic compounds), assigning oxidation numbers is still useful for tracking theoretical electron movement and predicting chemical behavior.
In CCl₄, carbon is surrounded by more electronegative chlorine atoms, so it “loses” electron density, making it more positively charged in oxidation number terms. The +4 state indicates that carbon is effectively giving up control of four electrons to the chlorine atoms.