An atom with a formal charge does not necessarily have more or less electron density than the atoms in the molecule without formal charges. We can see this by examining the potential maps for H2O, H3O+, and HO−.
a. Which atom bears the formal negative charge in the hydroxide ion? b. Which atom has the greater electron density in the hydroxide ion?

Verified step by step guidance

1. Identify the hydroxide ion (OH−) and its structure, which consists of an oxygen atom bonded to a hydrogen atom with a negative charge on the oxygen.
2. Determine the formal charge on each atom in the hydroxide ion. The oxygen atom has a formal negative charge because it has one more electron than its neutral state.
3. Analyze the electron density map for the hydroxide ion. The atom with the greater electron density will be the one with the higher concentration of electron clouds around it.
4. Compare the electron density around the oxygen and hydrogen atoms in the hydroxide ion. The oxygen atom, bearing the negative charge, will have a higher electron density.
5. Conclude that in the hydroxide ion, the oxygen atom bears the formal negative charge and also has the greater electron density.

Key Concepts

Formal Charge

Formal charge is a theoretical charge assigned to an atom in a molecule, calculated based on the number of valence electrons, the number of bonds, and the number of non-bonding electrons. It helps in understanding the distribution of electrons within a molecule and can indicate the stability of different resonance structures. A formal charge of -1 indicates that the atom has one more electron than it would in its neutral state.

Electron Density

Electron density refers to the probability of finding electrons in a particular region around an atom or within a molecule. It is visualized using electron density maps, which show areas of high and low electron concentration. Higher electron density often correlates with regions of negative charge, while lower density may indicate positive charge or less electron presence.

Resonance Structures

Resonance structures are different ways of drawing the same molecule that illustrate the delocalization of electrons. They help in understanding the actual electron distribution in a molecule, which may not be accurately represented by a single Lewis structure. The true structure is a hybrid of all possible resonance forms, affecting properties like stability and reactivity.