For the ion IF4+, draw its Lewis Structure and then answer the following questions base on that structure. (The central atom in each case is the atom with the lowest electronegativity). How many valence electrons are in the ion? (Remember to add an electron for each negative charge or to subtract one for each positive charge). How many lone pairs of electrons are in the central atom of the ion? What is the electron pair geometry of the ion? What is (are) the bond angle(s) at the central atom of the ion IF4+? Would the ion’s structure be polar, nonpolar, or ionic?
For the ion IF4+, draw its Lewis Structure and then answer the following questions base on that structure. (The central atom in each case is the atom with the lowest electronegativity). How many valence electrons are in the ion? (Remember to add an electron for each negative charge or to subtract one for each positive charge). How many lone pairs of electrons are in the central atom of the ion? What is the electron pair geometry of the ion? What is (are) the bond angle(s) at the central atom of the ion IF4+? Would the ion’s structure be polar, nonpolar, or ionic?
The Correct Answer and Explanation is:
Ion: IF₄⁺ – Analysis and Lewis Structure
1. Total Valence Electrons
- Iodine (I) has 7 valence electrons.
- Each fluorine (F) has 7 valence electrons × 4 = 28 electrons.
- The ion has a +1 charge, so we subtract 1 electron.
- Total valence electrons = 7 (I) + 28 (F) – 1 (positive charge) = 34 valence electrons
2. Lewis Structure
- Iodine (least electronegative) is the central atom.
- Connect 4 fluorine atoms to iodine with single bonds → uses 8 electrons (4 bonds × 2 e⁻ each).
- Distribute remaining 26 electrons (34 – 8) as lone pairs on F atoms (6 electrons per F × 4 = 24).
- 2 electrons remain → placed as a lone pair on iodine.
So, iodine has:
- 4 bond pairs (to 4 F atoms)
- 1 lone pair
3. Lone Pairs on Central Atom
- 1 lone pair on the central iodine atom.
4. Electron Pair Geometry
- With 5 regions of electron density (4 bonds + 1 lone pair), the electron pair geometry is trigonal bipyramidal.
5. Molecular Geometry
- Lone pair occupies an equatorial position, resulting in a see-saw molecular shape.
6. Bond Angles
- In a see-saw shape:
- Axial-F–I–equatorial bond angle ≈ 90°
- Equatorial-F–I–equatorial angle ≈ 120°
- Due to lone pair repulsion, angles are slightly less than 90° and 120°
7. Polarity
- The ion is polar because the lone pair causes asymmetry in electron distribution, making the dipoles not cancel.
8. Ionic or Covalent?
- While IF₄⁺ is an ion, the bonds are covalent, not ionic, because electrons are shared between iodine and fluorine.
Summary
- Valence electrons: 34
- Lone pairs on central atom: 1
- Electron pair geometry: Trigonal bipyramidal
- Bond angles: <90° and <120°
- Structure: Polar covalent ion
This detailed analysis reflects how electron configuration governs molecular shape, bond angles, and polarity.
