why are anions always larger than the atoms from which they are formed
Electrons added to the outer shell, all of them with a negative charge, means there are more repulsive forces, and that occupies more space.
why is the formula written for an ionic compound such as NaCl the empirtcal formula ,rather than a molecular formula?
thanks
Answered above.
An anion is a negatively charged ion that is formed when an atom gains one or more electrons. The reason why anions are usually larger than the atoms from which they are formed can be explained using the concept of electron-electron repulsion.
When an atom gains one or more electrons to become an anion, the added electrons occupy the outermost energy level or shell of the atom. The more electrons there are in the outer energy level, the stronger the repulsion between them. This repulsive force tends to push the electrons farther apart, making the electron cloud spread out.
As a result, the increase in electron-electron repulsion causes the overall size of the anion to be larger than the original atom. In other words, the added negative charge from extra electrons causes the electron cloud to expand, leading to an increase in the atomic radius.
It's important to note that this explanation is a simplification and doesn't account for all factors that can influence the size of an ions or atoms. Various factors such as the nuclear charge, effective nuclear charge, and electron shielding can also affect the size of anions and atoms. However, electron-electron repulsion is a significant factor in explaining why anions tend to be larger.