Which of the following molecules does not have a dipole moment?
1) CBr2=CBr2
2) NCl3
3) CH3NH2
4) HCl
To determine if a molecule has a dipole moment, we need to consider the polarity of its bonds and the molecular geometry.
A dipole moment occurs when there is an unequal distribution of electron density in a molecule, resulting in a separation of charge. In other words, the molecule has a positive end and a negative end.
To identify the molecule that does not have a dipole moment among the options given, let's go through them one by one:
1) CBr2=CBr2:
To determine the polarity, we need to consider the polarity of the C-Br bonds and the molecular geometry. Since both carbon-bromine bonds are polar, and the molecule has a symmetrical structure (central carbon atom with bromine atoms arranged in a tetrahedral shape), the dipole moments of the individual bonds cancel each other out. Therefore, this molecule does not have a net dipole moment.
2) NCl3:
Again, we examine the polarity of the N-Cl bonds and the molecular geometry. Nitrogen and chlorine have significantly different electronegativities, creating polar bonds. In the case of NCl3, it has a trigonal pyramidal structure with the nitrogen atom at the center and three chlorine atoms attached to it. Although the bond polarities do not cancel each other completely, the molecular geometry does not allow for a net dipole moment.
3) CH3NH2:
In this molecule, we have carbon-nitrogen and nitrogen-hydrogen bonds. The nitrogen-hydrogen bonds are polar, while the carbon-nitrogen bond is also polar due to the difference in electronegativity. The overall shape is pyramidal, with the nitrogen atom at the center and the carbon and hydrogen atoms attached to it. Once again, the bond polarities do not cancel each other out, resulting in a net dipole moment.
4) HCl:
In this case, the hydrogen-chlorine bond is highly polar due to the significant difference in electronegativity between hydrogen and chlorine. Additionally, the molecule has a linear structure, with the chlorine atom at one end and the hydrogen atom at the other end. Therefore, HCl has a net dipole moment.
Based on the explanations provided above, the molecule that does not have a dipole moment is option 1) CBr2=CBr2.