Anions and cations

If the atoms have a balanced number of electrons (negative charge) and protons (positive charge), they are generally neutral. However, if they are not balanced, they are called ions. Given this introduction, we will teach you what anions and cations are, and what are their differences . Read on for more information!




Load PositiveNegative
Electrode attracted by Cathode (negative)Anode (positive)
 Formed byMetal atomsNon-metallic atoms
ExamplesSodium (Na +), Iron (Fe2 +), Ammonium (NH4 +)Chloride (Cl-), bromide (Br-), sulfate (SO42-)

The metal atoms retain some of its electrons relatively loose manner. Consequently, they tend to lose electrons and form cations . In contrast, most non-metallic atoms attract electrons more strongly than metallic atoms, thus gaining electrons to form anions . Therefore, when the atoms of a metallic and a non-metallic element combine, the non-metallic atoms tend to extract one or more electrons from the metallic atoms to form ions. These oppositely charged ions attract each other to form ionic bonds and produce ionic compounds with no total net charge. Examples include calcium chloride (CaCl2), potassium iodide (KI), and magnesium oxide (MgO).

What is a cation

A cation has more protons than electrons, giving it a net positive charge . For a cation to form, one or more electrons must be lost, typically driven away by atoms with a stronger affinity for them. The amount of electrons lost, and therefore the charge of the ion, is indicated after the chemical symbol, for example silver (Ag) loses one electron to become Ag +, while zinc (Zn) loses two electrons to become in Zn2 ​​+.

What is an anion

An anion has more electrons than protons, which gives it a net negative charge . For an anion to form, one or more electrons must be obtained, typically distant from other atoms with a weaker affinity for them. The number of electrons gained, and therefore the charge of the ion, is indicated after the chemical symbol, for example chlorine (Cl) gains one electron to become Cl-, while oxygen (O) gains two electrons to become in O2-.

Periodic table cation vs anion

It may be possible to predict whether an atom will form a cation or an anion based on its position on the periodic table . Halogens always form anions, while alkali metals and alkaline earth metals always form cations. Most other metals form cations (eg iron, silver, nickel), while most other nonmetals usually form anions (eg oxygen, carbon, sulfur). However, some elements are capable of forming cations and anions under the right conditions. An example is hydrogen, which can gain (H-) or lose (H +) an electron, forming hydride compounds like ZnH2 (where it is an anion) and hydron compounds like H2O (where it is a cation).

The elements in group 18 of the periodic table, the “noble gases”, tend not to form ions due to the arrangement of their electrons that makes them generally non-reactive.

Using ionic properties

Chemists can exploit ionic properties for a variety of purposes. Chromatography ion exchange, for example, is based on the affinity of the molecules for the stationary phase separated according to their charge properties to allow separation.

Ionic properties are also critical to the function of batteries. Batteries have two electrodes made of conductive material, the cathode, which is the positive end where electric current goes out / electrons go in, and the anode where electric current goes in / electrons go out. Between the electrodes there is an electrolytic liquid or gel that contains charged particles – ions. As this ionic substance reacts with the electrodes, it generates electrical current. In single use, dry cell batteries, zinc is commonly used as the anode, while manganese dioxide is a popular choice for the electrolyte cathode. The zinc anode also acts as the battery container in zinc-carbon batteries, so as it oxidizes during use, the contents can start to leak over time.

A zinc-carbon dry cell battery (left) and an alkaline battery (right).

In rechargeable batteries , like many lithium-ion batteries, this chemical process is reversible and the internal structure is different, allowing the batteries to be recharged.

Due to the ionic properties of salt water, scientists are now striving to exploit the ionic electricity generating potential of salinity gradients where salt water and fresh water mix as a green source of power generation for the future.

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