To determine the valence electrons in NO2 (nitrogen dioxide), we need to consider the valence electrons of each atom in the molecule.
Nitrogen (N) is in Group 15 of the periodic table and has 5 valence electrons.
Oxygen (O) is in Group 16 and has 6 valence electrons. Since there are two oxygen atoms in NO2, we multiply this by 2.
Adding the valence electrons for nitrogen and oxygen gives us: 5 (valence electrons of nitrogen) + 2 × 6 (valence electrons of oxygen) = 17 valence electrons.
To determine the electron and molecular geometry of NO2, we use the valence shell electron pair repulsion (VSEPR) theory:
Electron Geometry: The central nitrogen atom is surrounded by two oxygen atoms. Considering the lone pairs and bonding pairs of electrons, the electron geometry of NO2 is "trigonal planar." The electron geometry refers to the arrangement of electron pairs around the central atom, including both bonding and lone pairs.
Molecular Geometry: The molecular geometry describes the arrangement of only the bonding pairs of electrons. In NO2, there is one lone pair of electrons on the central nitrogen atom, resulting in a bent or "angular" molecular geometry.
Regarding the polarity of NO2, we consider the molecular geometry and the electronegativity of the atoms:
The oxygen atoms in NO2 are more electronegative than the nitrogen atom. Since the molecule has a bent molecular geometry, the bond dipoles between the nitrogen and oxygen atoms do not cancel out. As a result, NO2 is a polar molecule, with a slight negative charge on the oxygen atoms and a slight positive charge on the nitrogen atom.