In a molecule with a square pyramidal molecular geometry, how many outer atoms and lone pairs are present around the central atom?

• A. 5 outer atoms and 1 lone pair
• B. 4 outer atoms and 2 lone pairs
• C. 6 outer atoms and 0 lone pairs
• D. 5 outer atoms and 0 lone pairs

Answer: (A)

Verified step by step guidance

1. Recall that the molecular geometry called 'square pyramidal' is derived from the electron geometry known as 'octahedral,' which involves six regions of electron density around the central atom.
2. In an octahedral arrangement, there are six positions around the central atom. To form a square pyramidal shape, one of these positions is occupied by a lone pair instead of an atom.
3. Therefore, the central atom in a square pyramidal molecule has five outer atoms bonded to it, arranged in a square base with one atom above the plane, forming the pyramid shape.
4. Since one of the six positions is taken by a lone pair, the central atom has exactly one lone pair of electrons.
5. Summarizing, a square pyramidal molecular geometry corresponds to 5 outer atoms bonded to the central atom and 1 lone pair of electrons on the central atom.