Which ion with a +1 charge has the electron configuration \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 3 d^{10} 4 s^{2} 4 p^{6} ?\) Which ion with \(a-2\) charge has this configuration?

The atomic number of an element is a fundamental concept in chemistry, representing the total number of protons in the nucleus of an atom. Since protons define the identity of an element, the atomic number is essentially the element's unique identifier on the periodic table.

Each element has a distinct atomic number, starting with hydrogen at 1 and increasing as we move across the periodic table. For a neutral atom, the number of protons is always equal to the number of electrons, ensuring an electrically neutral charge. An element's placement in the periodic table is determined by its atomic number, which also influences its chemical properties and behavior.

In the context of electron configurations, knowing the atomic number allows us to determine the number of electrons surrounding the nucleus. When solving problems about ion electron configurations, we infer the atomic number from the sum of electrons found in a complete electron configuration, as was done in the original exercise by adding up the electrons in each subshell.

Cations and anions are atoms or molecules that have gained or lost electrons, giving them a net positive or negative charge, respectively. Cations, which are positively charged, are formed when an atom loses one or more electrons. This process is often seen in metals, which have a propensity to give up electrons during chemical reactions.

Anions, on the other hand, carry a negative charge as a result of gaining extra electrons. Nonmetals typically form anions as they tend to accept electrons to achieve a full valence shell, following the octet rule. In a chemical reaction, the formation of cations and anions is driven by the need for atoms to reach a more stable electronic state.

Charge and Reactivity

The charge on cations and anions dictates their reactivity and ability to form ionic bonds. Ions with opposite charges attract each other, leading to the formation of ionic compounds, which have distinct properties compared to their neutral counterparts. It's important to note that an ion's charge also influences its electron configuration, as seen in the step-by-step solution for determining the +1 and -2 charged ions.

Electron subshell notation is a way to denote the arrangement of electrons around an atom's nucleus. This notation includes numbers and letters: the number indicates the electron's energy level (principal quantum number), and the letter represents the subshell type (s, p, d, or f), which corresponds to the shape of the electron's probable location.

Each subshell has a specific maximum number of electrons it can hold. For example, the 's' subshell can hold up to 2 electrons, the 'p' subshell can hold up to 6, the 'd' up to 10, and the 'f' subshell can hold up to 14 electrons. In the given exercise, the electron configuration includes the 's', 'p', and 'd' subshells, representing different energy levels and positions within an atom.

Subshell Filling Order

Electrons fill the subshells in a particular order, based on increasing energy levels. The Aufbau principle gives us the typical filling order, starting with the lowest energy level. However, in transition metals and beyond, this filling order can have exceptions due to the energy differences between subshells of different main energy levels. Understanding the electron subshell notation is crucial for predicting the chemical behavior of atoms and the types of ions they are likely to form when they gain or lose electrons.