Final answer:
Tetrahedral shape in molecules is determined by the tetrahedral arrangement of electron groups around a central atom as per VSEPR theory, optimizing electron repulsion. Methane (CH4) exemplifies such a structure with approximately 109.5° bond angles, whereas lone pairs in other molecules, like water (H2O), can create bent shapes despite a tetrahedral electronic arrangement.
Step-by-step explanation:
The tetrahedral shape of a molecule is determined by the arrangement of electron groups around the central atom. According to the VSEPR (Valence Shell Electron Pair Repulsion) theory, electron groups around the central atom repel each other and thus arrange themselves as far apart as possible. In the case of a molecule with four electron groups, this leads to a tetrahedral geometry.
An example of a tetrahedral molecule is methane (CH4). In methane, there are four hydrogen atoms, each bonded to a central carbon atom. The electron groups that consist of the bonding pairs of electrons repel each other and position themselves in three-dimensional space to form a tetrahedron, with angles of approximately 109.5°.
Other molecules with four electron regions also adopt a tetrahedral geometry for the electron-pair arrangement. However, the presence of lone pairs can affect the molecular shape, making it bent or angular, as seen in water (H2O). Here, the electron-pair geometry remains tetrahedral, but the presence of two lone pairs on the oxygen results in a molecular structure that is bent, with a bond angle smaller than 109.5°.