Cations and anions: concept, examples and ionic bonds

Cations and anions are types of ions, that is, atoms that have gained or lost electrons through chemical bonds.

An atom that has the same number of protons (positive charge) and electrons (negative charge) is considered electrically neutral. When this atom accepts or transfers electrons, it is called an ion which, in turn, can be:

• Cation: Atom that has lost (or given up) electrons and is therefore positively charged.
• Anion: Atom that has gained (or accepted) electrons and is therefore negatively charged.

Cation

A cation is an atom that has a positive charge because it has more protons than electrons.

Alkali metals (Lithium, Sodium, Potassium, Rubidium, Cesium and Francium) tend to form cations because they have only 1 electron in their valence shell. This means that the energy needed to remove this electron is very low, making these elements highly reactive.

A cation is represented by the symbol ⁺, following the element name. The amount of lost electrons indicates the type of cation:

• Cations with a +1 charge are called monovalents.
• Cations with a +2 charge are called bivalents.
• Cations with a +3 charge are called trivalents.

Cation types can also be identified by the amount of signals ⁺. Thus, an element represented only by ⁺ is a monovalent cation, while another represented by ⁺⁺⁺ is a trivalent cation.

Examples of cations

• Al⁺³ (Aluminum)
• Here⁺² (Calcium)
• mg⁺² (Magnesium)
• At⁺¹ (Sodium)
• K⁺¹ (Potassium)
• Zn⁺² (Zinc)
• Pb⁺⁴ (Lead)

anion

An anion is an atom that has a negative charge because it has more electrons than protons. The elements of the families of nitrogen, chalcogens and halogens tend to form anions because they are easy to accept electrons.

An anion is represented by the symbol ^-, following the element name. The amount of electrons received indicates the type of anion:

• Anions with a charge of -1 are called monovalents.
• Anions with a -2 charge are called bivalents.
• Anions with a -3 charge are called trivalents.

As with cations, anions can also be identified by the amount of signals ^-. Therefore, an element represented only by ^- is a monovalent anion, while another represented by ^{- -} is a bivalent anion.

Examples of anions

• O^-2 (Oxygen)
• N^-3 (Azide)
• F^-1 (Fluoride)
• br^-1 (Bromide)
• s^-2 (Sulfur)
• Cl^-1 (Chloride)

ionic bonds

Ionic bonds or electrovalent bonds are bonds that occur between cations and anions.

Elements can accept, give away or share electrons in such a way that their last energy shell has 8 electrons. This is known as the Octet Theory.

According to the Octet Theory, atoms tend to stabilize when there are 8 electrons in the valence shell (last electron shell). Thus, because they are positively charged, cations bind to negatively charged anions. In this way, atoms give up or accept electrons in order to achieve equilibrium.

The bonds formed between cations and anions are very strong and tend to have the following attributes:

• they are solid and brittle under normal conditions of temperature and pressure;
• have very high melting and boiling points;
• its best solvent is water;
• when dissolved in liquids, they conduct an electric current.

Ionic bonds give rise to ionic compounds, such as sodium chloride (table salt), formed by the Na bond⁺ (sodium cation) + Cl^- (chloride anion) → NaCl.

Examples of ionic compounds

Some examples of ionic compounds are:

• NaCl - Sodium chloride (table salt)
• At₂ONLY₄ – Sodium sulfate
• CaCO₃ - Calcium carbonate
• NaNO₃ – Sodium nitrate

Cation table

read^+	Lithium	Faith^+2	Ferrous
At^+	Sodium	Co^+2	cobalt
K^+	Potassium	Ni^+2	nickel-plated
Rb^+	Rubidium	Yn^+2	tinny
Cs^+	Cesium	Pb^+2	Plumbus
(NH4)^+	Ammonium	Mn^+2	Mango
Ag^+	Silver	Pt^+2	platinum
Ass^+	Copper	Bi^+3	Bismuth
Hg^+	mercurial	Al^+3	Aluminum
Au^+	aurorous	Cr^+3	Chrome
mg^+2	Magnesium	Au^+3	Auric
Here^+2	Calcium	Faith^+3	ferric
Mr^+2	Strontium	Co^+3	Cobaltic
Ba^+2	Barium	Ni^+3	Nickelic
Zn^+2	Zinc	Yn^+4	Stannic
CD^+2	Cadmium	Pb^+4	Plumbic
Ass^+2	cupric	Mn^+4	manganic
Hg^+2	mercuric	Pt^+4	platinum

anion table

F^-	Fluoride	P2O7^-4	Pyrophosphate
Cl^-	Chloride	(AT THE2)^-	Nitrite
br^-	Bromide	(AT THE3)^-	Nitrate
I^-	Iodide	s^-2	Sulfide
(ClO)^-	Hypochlorite	(ONLY4)^-2	Sulfate
(CLO2)^-	Chlorite	(ONLY3)^-2	Sulfite
(CLO3)^-	Chlorate	(S2O3)^-2	Thiosulfate
(CLO4)^-	perchlorate	(S4O6)^-2	persulfate
(BrO)^-	Hypobromite	(MnO4)^-	Permanganate
(BrO3)^-	bromate	(MnO4)^-2	manganate
(IO)^-	hypoiodite	(SiO3)^-2	Metasilicate
(IO3)^-	Iodate	(SiO4)^-4	Orthosilicate
(IO4)^-	Periodate	(CrO4)^-2	chromate
(CN)^-	Cyanide	(CrO7)^-2	Dichromate
(CNO)^-	cyanate	(ASO3)^-3	arsenite
(CNS)^-	Thiocyanate	(ASO4)^-3	Arsenate
(Ç2H3O2)^-	Acetate	(SbO3)^-3	Antimony
(CO3)^-2	Carbonate	(SbO4)^-3	Antimonate
(Ç2O4)^-2	oxalate	(BO3)^-3	borate
[Fe(CN)6]^-3	Ferricyanide	(SnO3)^-2	stannate
[Fe(CN)6]^-4	ferrocyanide	(SnO2)^-2	tin
(DUST3)^-	Metaphosphate	(Hello2)^-	Aluminate
(H2DUST2)^-	Hypophosphite	(PbO^2)^-2	Plumbito
(HPO3)^-2	Phosphite	(ZnO2)^-2	Zinc
(DUST4)^-3	orthophosphate

See too:

• Molecule
• ions
• chemical energy
• Ionizing