Final answer:
The molecular structure around a central atom is determined by the number of bonded atoms and lone pairs, resulting in configurations such as linear, trigonal planar, tetrahedral, and octahedral.
Step-by-step explanation:
In chemistry, the molecular structure around a central atom can vary based on the number of bonded atoms and lone pairs of electrons. Key geometries include:
- Linear - This occurs when there are two regions of electron density around a central atom, resulting in a straight-line arrangement of atoms. An example of a molecule with a linear structure is carbon dioxide (CO2).
- Trigonal Planar - This structure is formed when there are three regions of electron density, leading to a flat triangular shape. An example is boron trifluoride (BF3).
- Tetrahedral - With four regions of electron density, atoms are positioned at the corners of a tetrahedron. Methane (CH4) has a tetrahedral shape.
- Octahedral - This complex geometry occurs with six regions of electron density around a central atom, like in sulfur hexafluoride (SF6). Each atom is at the corner of an octahedron.
The molecular structure may deviate from the electron-pair geometry due to the presence of lone pairs. For example, the presence of one or more lone pairs on the central atom can lead to bent, trigonal pyramidal, or other shapes that minimize electron pair repulsion.