NH2-, NH3, and NH4+ have H-N-H bond angles of 105, 107 and 109. Explain this variation in bond angles.

The difference lies in the number of lone pair electrons. Lone pair electrons take up more room than paired electrons; therefore, the atoms "on the other side" of the lone pair have less room and the angles are smaller. The NH4^+ has no unpaired electrons and the angle is that of a tetrahedral angle.

The variation in bond angles among NH2-, NH3, and NH4+ is due to the difference in their molecular geometries and electronic structures.

NH2- (Amide ion) has a bond angle of 105 degrees. In NH2-, the nitrogen atom is surrounded by two hydrogen atoms and one lone pair of electrons. The presence of the lone pair on nitrogen creates repulsion with the bonding pairs of electrons, causing the bond angles to deviate from the ideal tetrahedral angle of 109.5 degrees. The lone pair repulsion decreases the bond angle to 105 degrees.

NH3 (Ammonia) has a bond angle of 107 degrees. In NH3, the nitrogen atom is surrounded by three hydrogen atoms and one lone pair of electrons. Again, the lone pair repulsion affects the bond angles, causing them to be smaller compared to the ideal tetrahedral angle. However, the presence of three bonding pairs in NH3 instead of two in NH2- reduces the influence of the lone pair repulsion, resulting in a slightly larger bond angle of 107 degrees.

NH4+ (Ammonium ion) has a bond angle of 109 degrees. In NH4+, the nitrogen atom is bonded to four hydrogen atoms with no lone pair of electrons. Since there are no lone pairs, there is no repulsion from electron pairs and the bond angles will be close to the ideal tetrahedral angle of 109.5 degrees.

In summary, the variation in bond angles among NH2-, NH3, and NH4+ is due to the repulsion between lone pairs of electrons and bonding pairs, affecting the overall geometry and resulting in smaller bond angles as the number of lone pairs increases.

The variation in bond angles between NH2-, NH3, and NH4+ can be explained by considering the factors that influence the bond angles in molecules.

First, let's understand the concept of bond angles. Bond angles are the angles formed between two adjacent bonds in a molecule. They are determined by the presence of lone pairs and the repulsion between electron pairs.

NH2-: In the NH2- ion, there are three regions of electron density, consisting of two bonding pairs and one lone pair of electrons. According to VSEPR (Valence Shell Electron Pair Repulsion) theory, these electron pairs repel each other, causing the bond angles to be slightly smaller than the ideal angle of 109.5 degrees for a tetrahedral arrangement. The presence of the lone pair exerts higher repulsion than the bonding pairs, resulting in a decrease in the bond angle to 105 degrees.

NH3: In the NH3 molecule, there are also three regions of electron density, but this time, all three are bonding pairs and there are no lone pairs. The bonding pairs repel each other, pushing the atoms slightly apart and increasing the bond angle to around 107 degrees. Again, this is slightly smaller than the ideal tetrahedral angle due to repulsion between electron pairs.

NH4+: In the NH4+ ion, all four regions of electron density are bonding pairs with no lone pairs. Since there are no lone pairs to cause additional repulsion, the bonding pairs are able to spread out further from each other, resulting in a larger bond angle. The bond angle in NH4+ is closer to the ideal tetrahedral angle of 109.5 degrees and measures around 109 degrees.

To summarize, the variation in bond angles between NH2-, NH3, and NH4+ is due to the repulsion between electron pairs. The presence of a lone pair in NH2- causes a decrease in the bond angle, while the absence of lone pairs in NH3 and NH4+ allows the bond angles to increase.

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