The bar on the first nitrogen surface represents a pair of electrons, for example, hydrogen has only one single electron, and n has a pair of electrons and three single electrons (only for the outermost layer). The following+is the same as the first picture, which has been explained, but not explained.
The coordination bond N-H is formed by the coordination of N and H+, where N provides a pair of electrons, that is, the bar you see, and H+ has no electrons, providing a free orbit (that is, a space for electrons).
Common valence bonds N-H are that they provide a single electron, and coordination bonds provide a pair of electrons on one side and an empty orbit on the other.
If you are interested, it is good to study structural chemistry and understand the theory of orbital and valence bond, but it is meaningless to the college entrance examination itself. The college entrance examination for organic chemistry is very simple, and the atomic structure part is simpler than the organic part. Just a few questions. If you want to further your studies in the university, or have hobbies, it is also good to have a look without affecting the review of other knowledge points. Bonding theory and coordination compounds are very interesting.