A metal ion with a net +3 charge has five electrons in the \(3 \mathrm{~d}\) subshell. Identify the metal.

Understanding metal ion electron configuration is essential in chemistry, especially when dealing with transition metals. Ions are atoms that have gained or lost electrons, and metal ions typically lose electrons, thus carrying a positive charge.

For instance, a metal ion with a +3 charge has given up three electrons. If this ion now has five electrons in its 3d subshell, we must consider what the electron configuration of the neutral atom looked like. In our case, five 3d electrons in the ion implies there were originally eight 3d electrons. Electron configuration thus helps us trace back to the element's identity on the periodic table.

The periodic table is the roadmap of elements, illustrating their properties based on atomic structure. The elements are arranged in periods (rows) and groups (columns), with transition metals located in the middle of the table.

Each period correlates with the highest principle energy level of an atom's electrons that gets filled. For example, the 3d subshell corresponds to elements in the fourth period. This interconnection between the electronic structure and the periodic table layout enables us to locate elements by their electron configuration.

Transition metals possess distinctive traits that differ from other elements. Here are some key characteristics:

• They are typically malleable and have high densities and melting points.
• Their valence electrons are in d-orbitals, which leads to a range of possible oxidation states.
• They form colored compounds and are good conductors of heat and electricity.
• Many transition metals are catalytically active, playing a crucial role in industrial processes.

Understanding these properties allows chemists to predict a transition metal's behavior in reactions and its use in practical applications.

Atomic structure refers to the arrangement of electrons, protons, and neutrons within an atom. Electrons are found in energy levels or shells around the nucleus and are further organized into subshells (s, p, d, and f).

The specific arrangement of electrons in these subshells is what we call electron configuration. For transition metals, the arrangement of electrons in the d subshell is particularly complex and important in determining the chemical behavior of the atom. In our exercise example, the 3d subshell plays a crucial role in identifying the element Nickel based on its atomic structure.

The oxidation state of an atom is a measure of the degree of its oxidation or reduction; it is the hypothetical charge an atom would have if all bonds to atoms of different elements were 100% ionic. Transition metals are known for having multiple possible oxidation states because they can lose different numbers of d electrons.

The +3 charge on a metal ion indicates it has lost three of its valence electrons, and the oxidation state helps chemists understand elements' reactivity, stability, and the types of compounds they can form. By determining the oxidation state, we deduce the electron count before ionization, as illustrated in the exercise where Nickel's 3+ state leads to its identification.