Final answer:
The Lewis structures and molecular formulas provided allow us to predict that the first molecule is linear, and assuming a representation of BH3, the second molecule is trigonal planar. CBr4 is tetrahedral, and BeH2 is linear in shape.
Step-by-step explanation:
The molecular shape of a molecule can be determined using the Valence Shell Electron Pair Repulsion (VSEPR) theory, which considers the repulsion between electron pairs to predict the arrangement of atoms. Lewis structures are useful for visualizing the placement of electrons and the geometrical arrangement of atoms in a molecule.
- For the molecule with the Lewis structure H-C≡N:, the shape is linear because of the triple bond between carbon and nitrogen, with hydrogen attached to carbon.
- The molecule with the Lewis structure H H:B:H has a trigonal planar shape, assuming this represents BH3 with boron having three bonding pairs of electrons.
- A molecule with the formula CBr4 has a tetrahedral shape because carbon is bonded to four bromine atoms symmetrically arranged around it.
- A molecule with the formula BeH2 has a linear shape because beryllium has two bonded electron pairs with no lone electron pairs on the central atom.