Anion

Definition

An anion is a negatively charged ion that is formed when an atom gains one or more electrons. This gain of electrons gives the anion a net negative charge, which is crucial in the formation of ionic bonds, where anions pair with positively charged ions, known as cations, to create stable compounds.

5 Must Know Facts For Your Next Test

1. Anions are typically formed from nonmetals, such as chlorine and oxygen, which have high electronegativities and readily gain electrons.
2. The charge of an anion is usually indicated by adding a suffix like '-ide', '-ate', or '-ite' to the element's name, for example, chloride (Cl⁻) or sulfate (SO₄²⁻).
3. Anions can also be polyatomic ions, which are composed of multiple atoms covalently bonded together, such as nitrate (NO₃⁻) and phosphate (PO₄³⁻).
4. In ionic compounds, the ratio of cations to anions is determined by their charges to ensure overall electrical neutrality in the compound.
5. The size of an anion is larger than its neutral atom due to electron-electron repulsion in the additional electron cloud.

Review Questions

• How do anions differ from cations in terms of their formation and charge?
  • Anions differ from cations primarily in their formation process and charge. Anions are formed when atoms gain electrons, resulting in a negative charge, whereas cations are produced when atoms lose electrons and acquire a positive charge. This difference in electron behavior is crucial for understanding how ionic bonds are formed, as anions and cations are attracted to each other due to their opposite charges.
• Discuss the role of electronegativity in determining which elements will form anions.
  • Electronegativity plays a significant role in determining which elements will form anions because it measures an atom's ability to attract and hold onto electrons. Elements with high electronegativity, such as halogens and oxygen, tend to gain electrons easily, resulting in the formation of anions. In contrast, elements with low electronegativity are more likely to lose electrons and form cations. Thus, understanding electronegativity helps predict the behavior of elements during ionic bonding.
• Evaluate the impact of anion size on the properties of ionic compounds they form.
  • The size of anions significantly impacts the properties of the ionic compounds they form. Larger anions can lead to weaker ionic bonds due to increased distance between the nuclei of the ions involved, reducing the strength of electrostatic attraction. This can affect properties like solubility and melting points. Additionally, smaller anions typically result in stronger ionic interactions due to their ability to get closer to the cation’s nucleus. Thus, analyzing anion size helps understand variations in the behavior of different ionic compounds.

Related terms

Cation: A cation is a positively charged ion that is formed when an atom loses one or more electrons.

Ionic Bonding: Ionic bonding is the electrostatic attraction that occurs between oppositely charged ions, typically between cations and anions.

Electronegativity: Electronegativity is a measure of an atom's ability to attract and hold onto electrons, influencing whether it will form cations or anions.