- Is H2O more or less polar than SCl2?
- Which of the following species (atoms or molecules) are free radicals? a. Br b. CH3 c. I
- Which of the following species (atoms or molecules) are free radicals? a. P b. CN c. SO2
The correct answer and explanation is:
1. Is H₂O more or less polar than SCl₂?
H₂O is more polar than SCl₂.
- Explanation: Polarity is determined by the molecular geometry and the electronegativity differences between atoms. H₂O is a bent molecule with a significant electronegativity difference between oxygen and hydrogen. Oxygen is highly electronegative, pulling the electron density towards itself and creating a strong dipole moment. The geometry of H₂O reinforces its polarity as the dipoles do not cancel out. On the other hand, SCl₂ is also bent, but sulfur and chlorine have a smaller electronegativity difference compared to oxygen and hydrogen. This results in weaker dipoles. Additionally, the larger size of sulfur and chlorine leads to less concentrated charge separation. Thus, H₂O exhibits greater polarity than SCl₂.
2. Which of the following species are free radicals?
a. Br
Yes, Br is a free radical.
Br (bromine atom) has an unpaired electron in its outermost shell, making it a free radical.
b. CH₃
Yes, CH₃ is a free radical.
The methyl radical (CH₃) is formed when one hydrogen atom is removed from methane (CH₄), leaving an unpaired electron on the carbon atom.
c. I
Yes, I is a free radical.
I (iodine atom) also has an unpaired electron in its outermost shell, classifying it as a free radical.
3. Which of the following species are free radicals?
a. P
No, P is not a free radical.
The phosphorus atom (P) typically forms stable bonds and does not have an unpaired electron in its most common states.
b. CN
Yes, CN is a free radical.
The cyanide radical (CN) contains an unpaired electron, making it a free radical.
c. SO₂
No, SO₂ is not a free radical.
SO₂ (sulfur dioxide) is a stable molecule with all electrons paired in its bonds and lone pairs.
Explanation
Free radicals are species with at least one unpaired electron in their electronic configuration. These species are typically highly reactive because they seek to pair their unpaired electron through chemical reactions. Elements like bromine (Br) and iodine (I) in their atomic forms are free radicals due to having an unpaired electron in their outermost p-orbital. Similarly, molecules like CH₃ and CN exhibit radical behavior because of an unpaired electron. Stable molecules such as SO₂ and P do not meet this criterion.