Dipole trigonal pyramidal

This molecule (type AB3U) has a tetrahedral electronic geometry and a trigonal pyramidal molecular geometry. The polar P-Cl bond dipoles oppose the effect of the lone pair. The molecule is polar. 

The N — F bonds are polar covalent. Due to the repulsive force of the lone pair electrons on the nitrogen atom the shape of the NF3 molecule is trigonal pyramidal. The dipole forces do not cancel each other out so the molecule is polar. 

The trigonal pyramidal molecular structure has been subjected to numerous interpretations. In Sc(btsa)3 the pyramidal ScN3 fragment was ascribed to crystal packing because the nonplanarity is lost in the gas phase [114a]. Electric dipole moment measurements confirmed a planarity in dilute benzene solutions [106a]. Zero dipole moments are also obtained for the larger lanthanide metals... 

The correct answer is (C). Bond dipoles can be treated as vector quantities or quantities with both a magnitude and a direction. Symmetric molecules, such as COz and BC13, have vectors that cancel each other out (as do the equal and opposite attractions between the diatomic Cl2). Only PC13, with its trigonal pyramidal shape, displays a net force or dipole moment. 

The molecular shape is trigonal pyramidal and it is a polar molecule. It can participate dipole-dipole interactions. 

The molecules NH3 and NF3 have trigonal pyramidal structures (1.17), and have dipole moments of 1.47 and... 

The gas-phase structure of NF3 is trigonal pyramidal (14.20), and the molecular dipole moment is very small (Table 14.5). In contrast to NH3 and PF3, NF3 shows no donor properties. 

Solution (a) For NH3. The molecular shape is trigonal pyramidal. From Figure 9.20, we see that N (EN = 3.0) is more electronegative than H (EN = 2.1), so the bond dipoles point toward N. The bond dipoles partially reinforce each other, and thus the molecular dipole points toward N ... 

SECTION 9.3 The dipole moment of a polyatomic molecule depends on the vector sum of the dipole moments associated with the individual bonds, called the bond dipoles. Certain molecular shapes, such as linear AB2 and trigonal planar AB3, assure that the bond dipoles cancel, producing a nonpolar molecule, which is one whose dipole moment is zero. In other shapes, such as bent AB2 and trigonal pyramidal AB3, the bond dipoles do not cancel and the molecule will be polar (that is, it will have a nonzero dipole moment). 

Consider an AB3 molecule in which A and B differ in electronegativity. You are told that the molecule has an overall dipole moment of zero. Which of the following could be the molecular geometry of the molecule (a) Trigonal pyramidal (b) Trigonal planar (c) T-shaped... 

Dipole Moments of Some Trigonal-Pyramidal Molecules ... 

Dipole moments for a number of trigonal-pyramidal molecules are given in Table 6-2. 

The molecules NH3 and NF3 have trigonal pyramidal structures (2.25), and have dipole moments of 1.47 and 0.24 D respectively. This significant difference may be rationalized by considering the bond dipole moments and the effects of the N lone pair. The values of x (N) and X (H) are 3.0 and 2.2, so each bond is polar in the sense. The... 

EXERCISE 103 Bromine trifluoride, Brp3, has a nonzero dipole moment. Indicate which of the following geometries are consistent with this information a. trigonal planar b. trigonal pyramidal c. T-shaped. 

Explain why nitrogen trifluoride has a small dipole moment even though it has polar bonds in a trigonal pyramidal arrangement. 

In molecules with two or more electron groups, the shape, such as bent or trigonal pyramidal, determines whether or not the dipoles cancel. For example, we have seen that H2O has a bent shape. Thus, a water molecule is polar because the individual dipoles do not cancel. 

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