The following observations are made about two hypothetical
elements A and B: The A¬A and B¬B bond lengths in the
elemental forms of A and B are 236 and 194 pm, respectively.
A and B react to form the binary compound AB2, which has
a linear structure (that is B-A-B = 180°). Based on these
statements, predict the separation between the two B nuclei
in a molecule of AB2.
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1
Identify the given bond lengths: A-A bond length is 236 pm and B-B bond length is 194 pm.
Understand the structure of the compound AB2, which is linear (B-A-B = 180°). This implies that the molecule is straight with atom A in the middle and two B atoms on either side.
Recognize that the separation between the two B nuclei in AB2 will be twice the length of the B-A bond since the molecule is linear.
Assume that the B-A bond length can be approximated by the average of the A-A and B-B bond lengths. Calculate this average: (236 pm + 194 pm) / 2.
Multiply the average bond length by 2 to find the separation between the two B nuclei in the AB2 molecule.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Bond Length
Bond length is the average distance between the nuclei of two bonded atoms. It is influenced by the types of atoms involved and the nature of the bond (single, double, or triple). In this case, the bond lengths of A-A and B-B provide insight into the size and strength of the bonds, which is essential for predicting the geometry and distances in the compound AB2.
Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule. The linear structure of AB2 indicates that the atoms are arranged in a straight line, with bond angles of 180°. Understanding molecular geometry is crucial for predicting the spatial relationships between atoms, which directly affects the separation between the B nuclei in the compound.
Valence Shell Electron Pair Repulsion (VSEPR) theory is a model used to predict the geometry of molecules based on the repulsion between electron pairs surrounding a central atom. In the case of AB2, the linear arrangement suggests that the two B atoms are positioned to minimize repulsion, leading to a specific separation that can be calculated using the bond lengths and the linear structure.
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