Caffeine is an organic compound that features a specific arrangement of carbon (C), nitrogen (N), hydrogen (H), and oxygen (O) atoms. To complete a Lewis structure for caffeine where all atoms have a formal charge of zero, we first need to identify the connectivity of the atoms based on its molecular formula, which is C8H10N4O2.
The Lewis structure shows that caffeine consists of three fused rings, including a six-membered aromatic ring and a five-membered ring containing nitrogen atoms. In total, there are 8 carbon atoms and 4 nitrogen atoms in caffeine’s structure.
To determine how many of these carbon and nitrogen atoms are sp² hybridized, we look at their bonding environments. In sp² hybridization, an atom has three regions of electron density, which typically means it forms three sigma bonds and has one unhybridized p orbital that can participate in pi bonding.
In caffeine, we find:
- 4 carbon atoms in the aromatic ring are sp² hybridized.
- 2 additional carbon atoms are also found in the aliphatic part of the molecule, which are sp² hybridized due to their connections.
- All 4 nitrogen atoms in caffeine are also sp² hybridized because they are bonded to carbon atoms and participate in resonance within the structure.
Thus, in total:
- There are 6 sp² hybridized carbon atoms.
- All 4 nitrogen atoms are also sp² hybridized.
In summary, the Lewis structure of caffeine can be drawn to show a total of 6 sp² hybridized carbon atoms and 4 sp² hybridized nitrogen atoms, fulfilling the requirement of zero formal charges on each atom, making the structure representative of typical organic compounds.