Question

What is the charge on the common monatomic ions of the following elements? (a) magnesium (b) zinc (c) nickel (d) gallium

Short answer

(a) Mg²⁺, (b) Zn²⁺, (c) Ni²⁺, (d) Ga³⁺

Step-by-step solution

Understand what a monatomic ion is

A monatomic ion is an ion consisting of exactly one atom. Common monatomic ions are formed by gaining or losing electrons to achieve a stable electron configuration similar to noble gases.

Determine the charge of magnesium's ion

Magnesium (Mg) is in Group 2 of the periodic table. Elements in this group have two valence electrons, and they commonly lose these electrons to achieve the stable electron configuration of the nearest noble gas, neon (Ne). Consequently, magnesium forms a cation with a +2 charge.

Determine the charge of zinc's ion

Zinc (Zn) is in the transition metals, specifically in Group 12. Zinc typically forms a +2 charge when it loses two electrons, achieving a pseudo-noble gas configuration.

Determine the charge of nickel's ion

Nickel (Ni) is also a transition metal. It can form several ions, but the most common monatomic ion for nickel is the Ni²⁺ ion.

Determine the charge of gallium's ion

Gallium (Ga) is in Group 13 of the periodic table. Elements in this group often form ions with a +3 charge by losing three electrons to achieve the electron configuration of the nearest noble gas, argon (Ar). Therefore, gallium typically forms a +3 ion.

Key concepts

Electron Configuration

Electron configuration refers to the distribution of electrons in an atom's orbitals. It's like a map that represents where each electron "lives" around an atom's nucleus. Electrons fill these orbitals in a way that minimizes the atom's energy. You can think of electron configuration as building blocks, starting from the closest orbital to the nucleus and moving outward. This arrangement follows a specific order guided by three primary rules:

• Aufbau Principle: Electrons occupy the lowest energy orbitals first.
• Pauli Exclusion Principle: No two electrons can have the same set of quantum numbers; essentially, an orbital can hold a maximum of two electrons with opposite spins.
• Hund's Rule: Every orbital in a subshell gets one electron before any orbital gets a second electron, to minimize electron-electron repulsions.

Electron configurations are often written using a notation that includes numbers and letters representing the energy levels and types of orbitals. Understanding electron configuration is fundamental in chemistry because it helps explain an element's reactivity and the type of ions it forms. For example, magnesium's electron configuration can be modified to more easily reach a stable state by adjusting the number of electrons it holds.

Cations

Cations are positively charged ions. They are formed when an atom loses one or more electrons. Think of cations as a person who's given away something of theirs—electrons—to achieve a balanced and stable state. This typically happens because the atom wants to achieve the electron configuration of the nearest noble gas, which is known for having full orbitals and a stable arrangement.

In terms of forming cations, metals tend to do this most easily. For instance:

• Magnesium (Mg): Loses two electrons to form a cation with a +2 charge, noted as Mg²⁺.
• Zinc (Zn): Also forms a +2 charge when it gives away two electrons.
• Gallium (Ga): Typically loses three electrons to form a Ga³⁺ ion.

The process of losing electrons and forming a cation is crucial because it helps the atom achieve a lower energy state, which is more stable.

Periodic Table Groups

The periodic table is organized into columns known as groups or families. Elements within the same group often share similar properties because they have the same number of valence electrons. This is significant because valence electrons determine how an element reacts and bonds with others.

Here are some insights into the groups relevant to the exercise problem:

• Group 2: Includes magnesium, which means it has two valence electrons. Elements in this group usually form ions with a +2 charge by losing these electrons.
• Group 12: Contains zinc, known for forming stable +2 cations.
• Group 13: Includes gallium, with three valence electrons. These elements often form a +3 cation to achieve stability.

Understanding periodic table groups helps predict how elements will behave and what kind of ions, like cations, they'll form. It plays a crucial role in the study of chemical reactions and compound formation.

Valence Electrons

Valence electrons are the outermost electrons in an atom and are key players in chemical bonding and reactivity. Because they are in the highest energy level, they are the first to interact with other atoms. The number of valence electrons significantly influences an element's properties and its tendency to form certain types of ions or bonds.

Here's how valence electrons influence the formation of cations:

• Magnesium (Mg): With two valence electrons, it tends to lose both, resulting in a +2 charged cation.
• Zinc (Zn): Although it is in a different group, it still commonly loses two electrons from its valence shell to form a +2 cation.
• Gallium (Ga): Has three valence electrons, usually resulting in forming a +3 cation after losing all three electrons.

By examining the number of valence electrons, chemists can predict not just the type of ion an element will form but also its reactivity. For instance, elements are more reactive if they can easily gain or lose electrons to achieve a full outer electron shell.