Predict the number of valence electrons present in each of the following atoms (include the outermost d-electrons: (a) \(\mathrm{N}\); (b) Ag; (c) \(\mathrm{Nb}\); (d) W.

The periodic table is a comprehensive chart that organizes all the known elements based on their atomic number, which is the number of protons in the nucleus of an atom. Elements are arranged in rows, called periods, and columns, known as groups. Understanding the structure of the periodic table can greatly simplify the process of predicting valence electrons.

The elements in the same group often share similar properties, including the number of valence electrons. Valence electrons are the outermost electrons of an atom and play a fundamental role in chemical bonding. For example, Group 1 elements have 1 valence electron, while Group 15 elements, like Nitrogen (N), have 5 valence electrons. This predictable pattern provides a shortcut to determine the valence electrons without always having to write out the electron configuration.

Transition metals are found in the d-block of the periodic table and have unique properties that differentiate them from other elements. These metals typically have an incomplete d subshell that can contribute to valence electrons when determining chemical reactivity. Unlike main group elements, the valence electrons in transition metals include not only the outermost s subshell electrons but also the d subshell electrons from the previous energy level.

For instance, Silver (Ag) is considered to have 11 valence electrons, despite being in Group 11, because it includes 10 d-electrons from the 4d subshell and 1 s-electron from the 5s subshell. This is an example of how the standard rule of elements in the same group having the same number of valence electrons doesn't always apply to transition metals, making them an interesting subject for further chemical study.

Electron configuration is the arrangement of electrons within an atom's orbitals, and it is crucial for understanding chemical behavior. It's like a map that shows the exact location of all the electrons. The electrons fill the orbitals in a specific order, generally starting with the lowest energy level and moving to higher ones, a pattern described by the Aufbau principle.

The electron configuration can determine the valence electrons of an element, which are responsible for an atom's ability to form bonds with other atoms. In transition metals, such as Niobium (Nb) and Tungsten (W), the electron configuration is slightly more complex due to the d-electrons. For Nb, the electron configuration ends with 4d^4 5s^1, signifying 5 valence electrons (1 s-electron plus 4 d-electrons). Similarly, W ends with 5d^4 6s^2, indicating 6 valence electrons. This knowledge allows for the prediction of how atoms will interact with each other, playing a fundamental role in chemistry.