Consider the compound carbon tetraiodide, CI4 What is the total number of valence electrons in the molecule? How many bonding pairs of electrons are there? How many nonbonding electrons are there? What type of bond is the C-I bond? What is the polarity of the molecule
The Correct Answer and Explanation is:
In carbon tetraiodide (CI4), the central atom is carbon (C), and it is bonded to four iodine (I) atoms.
Total number of valence electrons:
- Carbon (C): Carbon is in group 14 of the periodic table, so it has 4 valence electrons.
- Iodine (I): Iodine is in group 17 of the periodic table, so each iodine atom has 7 valence electrons. There are four iodine atoms in CI4, contributing a total of 4 × 7 = 28 valence electrons.
Total valence electrons = 4 (from C) + 28 (from I) = 32 valence electrons.
Bonding pairs and nonbonding electrons:
In CI4, carbon forms four single bonds with four iodine atoms. Each single bond consists of a pair of electrons.
- Bonding pairs: There are 4 single bonds, and each bond involves 2 electrons. So, there are 4 bonding pairs.
- Nonbonding electrons: After the bonding pairs, each iodine atom has 3 lone pairs of electrons (6 electrons), because iodine is in group 17 and needs to complete its octet. Thus, there are 3 lone pairs per iodine atom, giving a total of 4 × 3 = 12 lone pairs, which means 24 nonbonding electrons in total.
Type of bond:
The bond between carbon and iodine is a polar covalent bond. Carbon and iodine have different electronegativities, with iodine being more electronegative than carbon. This difference in electronegativity causes the electron density to be pulled more towards iodine, creating a dipole where the iodine atom becomes partially negative (δ-) and the carbon atom becomes partially positive (δ+).
Polarity of the molecule:
Although the C-I bonds are polar, the overall molecule, CI4, is nonpolar. This is because the molecule is tetrahedral in shape, with the four iodine atoms symmetrically arranged around the central carbon atom. The individual bond dipoles cancel each other out due to the symmetry of the structure, resulting in no net dipole moment for the entire molecule.
In summary, CI4 has:
- 32 valence electrons,
- 4 bonding pairs,
- 24 nonbonding electrons,
- polar C-I bonds,
- and a nonpolar molecular structure due to symmetry.
