Define ionic and also molecular (covalent) compoundsPredict the kind of compound formed from elements based top top their place within the regular tableDetermine formulas for basic ionic compounds

In ordinary chemical reactions, the cell nucleus of every atom (and therefore the identification of the element) stays unchanged. Electrons, however, can be included to atoms by transport from various other atoms, lost by transfer to various other atoms, or common with various other atoms. The transfer and sharing of electrons amongst atoms administrate the chemistry the the elements. Throughout the development of some compounds, atoms acquire or lose electrons, and kind electrically charged particles referred to as ions (Figure 1).

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Figure 1. (a) A salt atom (Na) has actually equal numbers of protons and electrons (11) and also is uncharged. (b) A salt cation (Na+) has actually lost one electron, so it has one more proton (11) 보다 electrons (10), offering it an overall positive charge, signified through a superscripted add to sign.

You deserve to use the routine table come predict even if it is an atom will kind an anion or a cation, and also you can often predict the fee of the result ion. Atoms of plenty of main-group steels lose enough electrons to leave them through the same number of electrons together an atom the the coming before noble gas. To illustrate, one atom of an alkali metal (group 1) loses one electron and forms a cation with a 1+ charge; one alkaline planet metal (group 2) loses two electrons and forms a cation through a 2+ charge, and so on. Because that example, a neutral calcium atom, with 20 protons and also 20 electrons, conveniently loses two electrons. This outcomes in a cation with 20 protons, 18 electrons, and a 2+ charge. It has the same variety of electrons as atoms the the preceding noble gas, argon, and also is symbolized Ca2+. The name of a metal ion is the exact same as the name of the metal atom native which that forms, therefore Ca2+ is dubbed a calcium ion.

When atoms of nonmetal elements type ions, they normally gain enough electrons to provide them the same number of electrons as an atom that the next noble gas in the periodic table. Atom of team 17 acquire one electron and type anions with a 1− charge; atom of group 16 acquire two electron and kind ions through a 2− charge, and so on. Because that example, the neutral bromine atom, with 35 protons and 35 electrons, can get one electron to administer it v 36 electrons. This results in one anion through 35 protons, 36 electrons, and also a 1− charge. It has actually the same variety of electrons together atoms that the following noble gas, krypton, and also is symbolized Br−. (A discussion of the theory sustaining the favored condition of noble gas electron number reflected in these predictive rules because that ion formation is detailed in a later on chapter the this text.)

Note the usefulness that the routine table in predicting likely ion formation and also charge (Figure 2). Relocating from the far left come the right on the periodic table, main-group elements tend to form cations with a fee equal to the group number. That is, team 1 elements type 1+ ions; team 2 elements kind 2+ ions, and also so on. Moving from the much right to the left on the routine table, facets often type anions v a an unfavorable charge equal to the number of groups moved left indigenous the noble gases. Because that example, team 17 elements (one team left the the noble gases) kind 1− ions; team 16 facets (two groups left) type 2− ions, and so on. This trend have the right to be offered as a guide in numerous cases, however its predictive worth decreases when moving toward the center of the regular table. In fact, shift metals and some other metals frequently exhibit variable charges that are not predictable by their location in the table. For example, copper can kind ions v a 1+ or 2+ charge, and also iron can kind ions through a 2+ or 3+ charge.

Figure 2. Some aspects exhibit a continuous pattern that ionic charge once they kind ions.

Example 1

Composition that IonsAn ion discovered in some compounds supplied as antiperspirants has 13 protons and 10 electrons. What is that is symbol?

SolutionBecause the variety of protons remains unchanged once an atom creates an ion, the atomic variety of the element must it is in 13. Discovering this lets us use the regular table to identify the facet as Al (aluminum). The Al atom has lost three electrons and also thus has three an ext positive dues (13) 보다 it has actually electrons (10). This is the aluminum cation, Al3+.

Check her LearningGive the symbol and also name because that the ion v 34 protons and also 36 electrons.

Example 2

Formation of IonsMagnesium and also nitrogen react to type an ionic compound. Guess which develops an anion, which creates a cation, and also the fees of every ion. Create the symbol for each ion and name them.

SolutionMagnesium’s position in the periodic table (group 2) tells us that the is a metal. Metals form positive ion (cations). A magnesium atom must shed two electrons to have the same number electrons as an atom of the previous noble gas, neon. Thus, a magnesium atom will form a cation through two under electrons 보다 protons and also a fee of 2+. The symbol because that the ion is Mg2+, and it is called a magnesium ion.

Nitrogen’s position in the routine table (group 15) reveals the it is a nonmetal. Nonmetals kind negative ion (anions). A nitrogen atom must gain three electrons to have the same variety of electrons together an atom the the following noble gas, neon. Thus, a nitrogen atom will form an anion v three more electrons than protons and a charge of 3−. The symbol for the ion is N3−, and also it is dubbed a nitride ion.

Check your LearningAluminum and carbon reaction to kind an ionic compound. Suspect which develops an anion, which creates a cation, and also the charges of each ion. Compose the symbol for each ion and name them.


Al will type a cation through a fee of 3+: Al3+, one aluminum ion. Carbon will type an anion through a fee of 4−: C4−, a carbide ion.

The ions that we have debated so much are called monatomic ions, the is, they are ions formed from just one atom. We additionally find numerous polyatomic ions. This ions, i beg your pardon act as discrete units, room electrically fee molecules (a team of external inspection atoms v an all at once charge). Several of the an ext important polyatomic ions are listed in Table 6. Oxyanions are polyatomic ion that save on computer one or an ext oxygen atoms. In ~ this suggest in your examine of chemistry, you need to memorize the names, formulas, and also charges that the most typical polyatomic ions. Due to the fact that you will use them repeatedly, they will soon end up being familiar.

NameFormulaRelated AcidFormula
ammonium extNH_4^;;+
hydronium extH_3 extO^+
oxide extO_2^;;-
peroxide extO_2^;;2-
hydroxide extOH^-
acetate extCH_3 extCOO^-acetic acid extCH_3 extCOOH
cyanide extCN^-hydrocyanic acid extHCN
azide extN_3^;;-hydrazoic acid extHN_3
carbonate extCO_3^;;2-carbonic acid extH_2 extCO_3
bicarbonate extHCO_3^;;-
nitrate extNO_3^;;-nitric acid extHNO_3
nitrite extNO_2^;;-nitrous acid extHNO_2
sulfate extSO_4^;;2-sulfiric acid extH_2 extSO_4
hydrogen sulfate extHSO_4^;;-
sulfite extSO_3^;;2-sulfurous acid extH_2 extSO_3
hydrogen sulfite extHSO_3^;;-
phosphate extPO_4^;;3-phosphoric acid extH_3 extPO_4
hydrogen phosphate extHPO_4^;;2-
dihydrogen phosphate extH_2 extPO_4^;;-
perchlorate extClO_4^;;-perchloric acid extHClO_4
chlorate extClO_3^;;-chloric acid extHClO_3
chlorite extClO_2^;;-chlorous acid extHClO_2
hypochlorite extClO^-hypochlorous acid extHClO
chromate extCrO_4^;;2-chromic acid extH_2 extCr_2 extO_4
dichromate extCr_2 extO_7^;;2-dichromic acid extH_2 extCr_2 extO_7
permanganate extMnO_4^;;-permanganic acid extHMnO_4
Table 6. common Polyatomic Ions

Note the there is a device for naming some polyatomic ions; -ate and -ite space suffixes designating polyatomic ions containing more or fewer oxygen atoms. Per- (short for “hyper”) and also hypo- (meaning “under”) are prefixes an interpretation more oxygen atoms 보다 -ate and fewer oxygen atoms than -ite, respectively. Because that example, perchlorate is ClO4−, chlorate is ClO3−, chlorite is ClO2− and also hypochlorite is ClO−. Unfortunately, the number of oxygen atoms matching to a provided suffix or prefix is not consistent; for example, nitrate is NO3− while sulfate is SO42−. This will certainly be covered in an ext detail in the next module top top nomenclature.

The nature that the attractive pressures that host atoms or ions together within a link is the basis because that classifying chemistry bonding. As soon as electrons room transferred and also ions form, ionic bonds result. Ionic bonds room electrostatic forces of attraction, the is, the attractive forces experienced in between objects of opposite electric charge (in this case, cations and also anions). Once electrons space “shared” and molecules form, covalent bonds result. Covalent bonds space the attractive forces in between the positively fee nuclei that the bonded atoms and also one or much more pairs of electrons that room located between the atoms. Compounds room classified together ionic or molecular (covalent) ~ above the basis of the bonds existing in them.

Ionic Compounds

When an aspect composed of atoms that readily shed electrons (a metal) reacts v an aspect composed of atoms that readily obtain electrons (a nonmetal), a carry of electrons usually occurs, producing ions. The compound formed by this deliver is stabilized by the electrostatic attractions (ionic bonds) between the ions of the opposite charge present in the compound. For example, when each sodium atom in a sample that sodium metal (group 1) gives up one electron to type a sodium cation, Na+, and each chlorine atom in a sample the chlorine gas (group 17) accepts one electron to form a chloride anion, Cl−, the result compound, NaCl, is written of sodium ions and also chloride ion in the ratio of one Na+ ion for each Cl− ion. Similarly, each calcium atom (group 2) can offer up 2 electrons and transfer one to every of 2 chlorine atoms to kind CaCl2, which is composed of Ca2+ and also Cl− ion in the proportion of one Ca2+ ion to two Cl− ions.

A link that consists of ions and also is hosted together by ionic bonds is called an ionic compound. The periodic table can assist us recognize numerous of the link that space ionic: when a metal is combined with one or an ext nonmetals, the link is usually ionic. This pointer works well for predicting ionic compound formation for many of the compounds generally encountered in an introduce chemistry course. However, the is not always true (for example, aluminum chloride, AlCl3, is no ionic).

You can regularly recognize ionic compounds since of their properties. Ionic compounds room solids that commonly melt at high temperatures and also boil in ~ even higher temperatures. For example, salt chloride melts in ~ 801 °C and also boils at 1413 °C. (As a comparison, the molecular compound water melts in ~ 0 °C and also boils at 100 °C.) In heavy form, an ionic link is no electrically conductive since its ions are unable to flow (“electricity” is the circulation of charged particles). When molten, however, it have the right to conduct electricity since its ions room able to move freely through the liquid (Figure 3).

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Figure 3. sodium chloride melts at 801 °C and also conducts electricity when molten. (credit: modification of job-related by note Blaser and also Matt Evans)