1. In three dimensions, what is the greatest angle that can be achieved between

Question

1. In three dimensions, what is the greatest angle that can be achieved between four equivalent bonds? Formatting help: Just enter a number like 231.12, do not include "degrees".

2.central atom is found to have one double bond, one single bond, and one non-bonding pair of electrons. How many electron domains does the central atom have?

3.When determining the molecular geometry of a molecule, which of the following needs to be considered? Choose all that apply A. Number of bonding domains on the central atom. B. Number of non-bonding electron pairs on the central atom. C. Number of core electrons on the central atom. D. Number of unpaired valence electrons in the central atom.

Explanation / Answer

1. If an atom has four equivalent bonds, assuming that it lacks any non-bonding electron pairs, each bonding domain will repel the others equally. Such a situation results in a tetrahedral geometry. An ideal tetrahedral atom will the greatest bond angle for four equivalent bonds thus and that angle will be 109.5. A typical example is methane or any tetrahedral silane or hydrocarbon.

2. Electron domains are the sum total of the bonding electrons and non-bonding pairs. For every double bond, there will be two bonding domains - one for each bond as each of the two bonds in a double bond will be the result of overlap of different orbitals, possessing different energies. Then, one domain for every single bond and only one domain for every lone pair or non-bonding domain as each non-bonding domain is a pair of electrons on the same orbital that has energy or symmetry mismatch with orbitals of the incoming atoms preventing them from participating in bonding. Therefore, for a central atom with one double bond, one single bond and one non-bonding pair of electrons, there will be four electron domains. A typical example of such an atom is the N atom in imines, oximes, etc.

3. To determine the molecular geometry of any molecule, primarily the no.of electrons on the valence shell of the central atom needs to be determined as this will help elucidate the number of atoms that can bond to it and the greatest and least possible bond angles possible thus giving a rough idea of the geometry. Next, the no.of non-bonding domains need to determined as these will reduce the bonding situations possible and also increase the repulsion between bonded electrons on the central and thus decrease the possible bond angles. The core atoms in a central atoms however, do not play any role in determining the molecular geometry as they comprise of fully-filled orbitals that are already stabilized and do not participate in any bonding or anti-bonding situations but simply stay in the atom, determining the ionization energy, electron-affinity and effective nuclear charge felt by the valence electrons. So, to figure out the molecular geometry, A. Number of bonding domains on the central atom; B. Number of non-bonding electron pairs on the central atom and D. Number of unpaired valence electrons in the central atom alone need to be considered.

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