Learning Objectives

Know how ions create. Find Out the characteristic charges that ions have actually. Construct a appropriate formula for an ionic compound. Geneprice a proper name for an ionic compound.

So far, we have disputed facets and compounds that are electrically neutral. They have actually the exact same variety of electrons as prolots, so the negative charges of the electrons is well balanced by the positive charges of the protons. However before, this is not constantly the situation. Electrons can move from one atom to another; as soon as they perform, species via in its entirety electric charges are developed. Such species are referred to as ionsA species with an all at once electric charge.. Species through in its entirety positive charges are termed cationsA species with an all at once positive charge., while species via in its entirety negative charges are referred to as anionsA species through an as a whole negative charge.. Remember that ions are formed just as soon as electrons relocate from one atom to another; a proton never moves from one atom to another. Compounds created from positive and negative ions are called ionic compoundsA compound created from positive and also negative ions..

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Individual atoms have the right to gain or lose electrons. When they execute, they come to be monatomic ions. When atoms get or lose electrons, they usually get or lose a characteristic variety of electrons and so take on a characteristic overall charge. Table 3.6 "Monatomic Ions of Various Charges" lists some common ions in regards to just how many type of electrons they lose (making cations) or obtain (making anions). There are numerous things to notice around the ions in Table 3.6 "Monatomic Ions of Various Charges". First, each aspect that forms cations is a steel, except for one (hydrogen), while each element that develops anions is a nonmetal. This is actually among the chemical properties of metals and nonmetals: steels tfinish to develop cations, while nonsteels tend to develop anions. 2nd, many atoms develop ions of a solitary characteristic charge. When sodium atoms form ions, they always develop a 1+ charge, never a 2+ or 3+ or even 1− charge. Therefore, if you commit the indevelopment in Table 3.6 "Monatomic Ions of Various Charges" to memory, you will always know what charges the majority of atoms develop. (In Chapter 9 "Chemical Bonds", we will comment on why atoms create the charges they do.)

Table 3.6 Monatomic Ions of Various Charges

Ions developed by shedding a single electron H+
Ions created by shedding two electrons Mg2+
Ions formed by shedding 3 electrons Sc3+
Ions created by losing 4 electrons Ti4+
Ions formed by obtaining a single electron F−
Ions created by getting two electrons O2−
Ions developed by gaining three electrons N3−

Third, tright here are some exceptions to the previous suggest. A few aspects, all steels, have the right to develop more than one possible charge. For example, iron atoms can create 2+ cations or 3+ cations. Cobalt is one more element that deserve to form more than one feasible charged ion (2+ and also 3+), while lead have the right to form 2+ or 4+ cations. Unfortunately, tbelow is bit expertise which two charges a metal atom may take, so it is finest to just memorize the feasible charges a details aspect have the right to have actually.

Keep in mind the convention for indicating an ion. The magnitude of the charge is listed as a best supermanuscript next to the symbol of the aspect. If the charge is a single positive or negative one, the number 1 is not written; if the magnitude of the charge is greater than 1, then the number is composed before the + or − authorize. An facet symbol without a charge created next to it is assumed to be the uncharged atom.

Naming an ion is straightforward. For a cation, simply use the name of the element and include the word ion (or if you want to be more particular, add cation) after the element’s name. So Na+ is the sodium ion; Ca2+ is the calcium ion. If the facet has actually more than one possible charge, the worth of the charge comes after the element name and before the word ion. Therefore, Fe2+ is the iron two ion, while Fe3+ is the iron three ion. In print, we usage romale numerals in parentheses to recurrent the charge on the ion, so these two iron ions would be stood for as the iron(II) cation and the iron(III) cation, respectively.

For a monatomic anion, usage the stem of the facet name and also appfinish the sufdeal with -ide to it, and then add ion. This is similar to just how we named molecular compounds. Thus, Cl− is the chloride ion, and N3− is the nitride ion.

Example 6

Name each species.

O2− Co Co2+


This species has actually a 2− charge on it, so it is an anion. Anions are called using the stem of the aspect name through the sufresolve -ide added. This is the oxide anion. Since this species has no charge, it is an atom in its elemental form. This is cobalt.

Test Yourself

Name each species.

P3− Sr2+


the phosphide anion the strontium cation

Chemical formulas for ionic compounds are dubbed ionic formulasThe chemical formula for an ionic compound.. A proper ionic formula has actually a cation and an anion in it; an ionic compound is never created in between two cations just or 2 anions just. The essential to composing appropriate ionic formulas is simple: the complete positive charge must balance the full negative charge. Due to the fact that the charges on the ions are characteristic, sometimes we have to have even more than among a cation or an anion to balance the in its entirety positive and negative charges. It is standard to use the lowest ratio of ions that are needed to balance the charges.

For example, think about the ionic compound in between Na+ and also Cl−. Each ion has a single charge, one positive and one negative, so we require only one ion of each to balance the overall charge. When writing the ionic formula, we follow 2 additional conventions: (1) create the formula for the cation initially and the formula for the anion following, however (2) execute not compose the charges on the ions. Thus, for the compound between Na+ and Cl−, we have the ionic formula NaCl (Figure 3.5 "NaCl = Table Salt"). The formula Na2Cl2 likewise has actually well balanced charges, but the convention is to use the lowest proportion of ions, which would certainly be among each. (Remember from our conventions for creating formulas that we don’t compose a 1 submanuscript if tbelow is just one atom of a details facet present.) For the ionic compound between magnesium cations (Mg2+) and also oxide anions (O2−), aacquire we require just one of each ion to balance the charges. By convention, the formula is MgO.

For the ionic compound between Mg2+ ions and also Cl− ions, we now consider the truth that the charges have actually different magnitudes, 2+ on the magnesium ion and 1− on the chloride ion. To balance the charges through the lowest number of ions possible, we must have actually two chloride ions to balance the charge on the one magnesium ion. Rather than create the formula MgClCl, we incorporate the 2 chloride ions and compose it via a 2 subscript: MgCl2.

What is the formula MgCl2 informing us? Tbelow are two chloride ions in the formula. Although chlorine as an facet is a diatomic molecule, Cl2, elepsychological chlorine is not part of this ionic compound. The chlorine is in the form of a negatively charged ion, not the neutral element. The 2 subscript is in the ionic formula because we need 2 Cl− ions to balance the charge on one Mg2+ ion.

Example 7

Write the proper ionic formula for each of the 2 provided ions.

Ca2+ and Cl− Al3+ and F− Al3+ and O2−


We need 2 Cl− ions to balance the charge on one Ca2+ ion, so the correct ionic formula is CaCl2. We need three F− ions to balance the charge on the Al3+ ion, so the proper ionic formula is AlF3. With Al3+ and O2−, note that neither charge is a perfect multiple of the other. This suggests we need to go to a least common multiple, which in this instance will certainly be 6. To gain a total of 6+, we need two Al3+ ions; to gain 6−, we require three O2− ions. Hence the correct ionic formula is Al2O3.

Test Yourself

Write the proper ionic formulas for each of the two given ions.

Fe2+ and S2− Fe3+ and S2−


FeS Fe2S3

Naming ionic compounds is simple: integrate the name of the cation and also the name of the anion, in both instances omitting the word ion. Do not use numerical prefixes if tright here is even more than one ion vital to balance the charges. NaCl is sodium chloride, a combination of the name of the cation (sodium) and also the anion (chloride). MgO is magnesium oxide. MgCl2 is magnesium chloride—not magnesium dichloride.

In naming ionic compounds whose cations have the right to have actually even more than one feasible charge, we need to also encompass the charge, in parentheses and in roguy numerals, as part of the name. Hence FeS is iron(II) sulfide, while Fe2S3 is iron(III) sulfide. Aacquire, no numerical prefixes show up in the name. The number of ions in the formula is dictated by the should balance the positive and also negative charges.

Example 8

Name each ionic compound.

CaCl2 AlF3 Co2O3


Using the names of the ions, this ionic compound is named calcium chloride. It is not calcium(II) chloride because calcium develops only one cation once it develops an ion, and it has a characteristic charge of 2+. The name of this ionic compound is aluminum fluoride. We know that cobalt deserve to have actually even more than one feasible charge; we just have to identify what it is. Oxide always has a 2− charge, so via 3 oxide ions, we have actually a total negative charge of 6−. This indicates that the 2 cobalt ions have to contribute 6+, which for two cobalt ions indicates that each one is 3+. Thus, the correct name for this ionic compound is cobalt(III) oxide.

Test Yourself

Name each ionic compound.

Sc2O3 AgCl


scandium oxide silver chloride

How do you recognize whether a formula—and by expansion, a name—is for a molecular compound or for an ionic compound? Molecular compounds develop between nonsteels and also nonsteels, while ionic compounds form in between metals and nonmetals. The periodic table (Figure 3.2 "A Simple Periodic Table") can be used to recognize which aspects are metals and nonmetals.

Tbelow also exists a group of ions that contain even more than one atom. These are dubbed polyatomic ionsAn ion that consists of more than one atom.. Table 3.7 "Typical Polyatomic Ions" lists the formulas, charges, and names of some common polyatomic ions. Only among them, the ammonium ion, is a cation; the rest are anions. Most of them likewise contain oxygen atoms, so sometimes they are described as oxyanions. Several of them, such as nitprice and also nitrite, and sulfate and sulfite, have incredibly equivalent formulas and names, so treatment should be taken to obtain the formulas and names correct. Note that the -ite polyatomic ion has actually one less oxygen atom in its formula than the -ate ion however through the same ionic charge.

Table 3.7 Usual Polyatomic Ions

Name Formula and also Charge   Name Formula and Charge
ammonium NH4+   hydroxide OH−
acetate C2H3O2−, or CH3COO− nitrate NO3−
bicarbonate (hydrogen carbonate) HCO3− nitrite NO2−
bisulfate (hydrogen sulfate) HSO4− peroxide O22−
carbonate CO32− perchlorate ClO4−
chlorate ClO3− phosphate PO43−
chromate CrO42− sulfate SO42−
cyanide CN− sulfite SO32−
dichromate Cr2O72− triiodide I3−

The naming of ionic compounds that contain polyatomic ions complies with the very same rules as the naming for various other ionic compounds: sindicate incorporate the name of the cation and also the name of the anion. Do not usage numerical prefixes in the name if tright here is even more than one polyatomic ion; the only exception to this is if the name of the ion itself has a numerical presolve, such as dichromate or triiodide.

Writing the formulas of ionic compounds has one important difference. If more than one polyatomic ion is needed to balance the as a whole charge in the formula, encshed the formula of the polyatomic ion in parentheses and compose the correct numerical subscript to the ideal and also outside the parentheses. Thus, the formula in between calcium ions, Ca2+, and nitrate ions, NO3−, is correctly composed Ca(NO3)2, not CaNO32 or CaN2O6. Use parentheses wbelow compelled. The name of this ionic compound is simply calcium nitrate.

Example 9

Write the appropriate formula and also give the appropriate name for each ionic compound created in between the 2 provided ions.

NH4+ and S2− Al3+ and PO43− Fe2+ and also PO43−


Because the ammonium ion has a 1+ charge and also the sulfide ion has actually a 2− charge, we need 2 ammonium ions to balance the charge on a single sulfide ion. Enclosing the formula for the ammonium ion in parentheses, we have (NH4)2S. The compound’s name is ammonium sulfide. Due to the fact that the ions have the very same magnitude of charge, we need just one of each to balance the charges. The formula is AlPO4, and also the name of the compound is aluminum phosphate. Neither charge is an accurate multiple of the various other, so we need to go to the least prevalent multiple of 6. To get 6+, we need three iron(II) ions, and also to gain 6−, we need 2 phosphate ions. The proper formula is Fe3(PO4)2, and also the compound’s name is iron(II) phosphate.

Test Yourself

Write the proper formula and also offer the proper name for each ionic compound formed between the 2 provided ions.

NH4+ and PO43− Co3+ and NO2−


(NH4)3PO4, ammonium phosphate Co(NO2)3, cobalt(III) nitrite

Food and Drink App: Sodium in Your Food

The element sodium, at least in its ionic develop as Na+, is a important nutrient for people to live. In fact, the huguy body is approximately 0.15% sodium, via the average perboy having actually one-twentieth to one-tenth of a kilogram in their body at any type of given time, largely in fluids exterior cells and in other bodily fluids.

Sodium is likewise present in our diet. The common table salt we use on our foodstuffs is an ionic sodium compound. Many kind of processed foodstuffs additionally contain considerable quantities of sodium included to them as a variety of ionic compounds. Why are sodium compounds supplied so much? Generally sodium compounds are inexpensive, yet, even more importantly, most ionic sodium compounds dissettle conveniently. This allows processed food manufacturers to add sodium-containing substances to food mixtures and also know that the compound will dissettle and distribute evenly throughout the food. Simple ionic compounds such as sodium nitrite (NaNO2) are added to cured meats, such as bacon and deli-style meats, while a compound dubbed sodium benzoate is included to many packaged foods items as a preservative. Table 3.8 "Some Sodium Compounds Added to Food" is a partial list of some sodium additives supplied in food. A few of them you may acknowledge after reading this chapter. Others you may not recognize, yet they are all ionic sodium compounds via some negatively charged ion likewise current.

Table 3.8 Some Sodium Compounds Added to Food

Sodium Compound Use in Food
Sodium acetate preservative, acidity regulator
Sodium adipate food acid
Sodium alginate thickener, vegetable gum, stabilizer, gelling agent, emulsifier
Sodium aluminum phosphate acidity regulator, emulsifier
Sodium aluminosilicate anticaking agent
Sodium ascorbate antioxidant
Sodium benzoate preservative
Sodium bicarbonate mineral salt
Sodium bisulfite preservative, antioxidant
Sodium carbonate mineral salt
Sodium carboxymethylcellulose emulsifier
Sodium citrates food acid
Sodium dehydroacetate preservative
Sodium erythorbate antioxidant
Sodium erythorbin antioxidant
Sodium ethyl para-hydroxybenzoate preservative
Sodium ferrocyanide anticaking agent
Sodium formate preservative
Sodium fumarate food acid
Sodium gluconate stabilizer
Sodium hydrogen acetate preservative, acidity regulator
Sodium hydroxide mineral salt
Sodium lactate food acid
Sodium malate food acid
Sodium metabisulfite preservative, antioxidant, bleaching agent
Sodium methyl para-hydroxybenzoate preservative
Sodium nitrate preservative, shade fixative
Sodium nitrite preservative, color fixative
Sodium orthophenyl phenol preservative
Sodium propionate preservative
Sodium propyl para-hydroxybenzoate preservative
Sodium sorbate preservative
Sodium stearoyl lactylate emulsifier
Sodium succinates acidity regulator, flavor enhancer
Sodium salts of fatty acids emulsifier, stabilizer, anticaking agent
Sodium sulfite mineral salt, preservative, antioxidant
Sodium sulfite preservative, antioxidant
Sodium tartrate food acid
Sodium tetraborate preservative

The usage of so many kind of sodium compounds in all set and also processed foodstuffs has alarmed some medical professionals and nutritionists. They argue that the average perboy consumes also much sodium from his or her diet. The average perboy demands only about 500 mg of sodium eincredibly day; a lot of world consume more than this—up to 10 times as much. Some researches have implicated raised sodium intake via high blood pressure; newer researches imply that the connect is questionable. However, tbelow has actually been a push to mitigate the amount of sodium the majority of human being ingest every day: prevent processed and manufactured foodstuffs, read labels on packaged foodstuffs (which encompass an indication of the sodium content), don’t oversalt foodstuffs, and use other herbs and also seasonings besides salt in food preparation.


Food labels encompass the amount of sodium per serving. This particular label shows that tright here are 75 mg of sodium in one serving of this specific food item.

Key Takeaways

Ions create as soon as atoms shed or get electrons. Ionic compounds have positive ions and negative ions. Ionic formulas balance the complete positive and negative charges. Ionic compounds have actually a simple mechanism of naming. Groups of atoms can have actually an as a whole charge and make ionic compounds.


Exordinary just how cations form.

Exordinary how anions develop.

Give the charge each atom takes as soon as it forms an ion. If even more than one charge is possible, list both.

K O Co

Give the charge each atom takes once it creates an ion. If more than one charge is possible, list both.

Ca I Fe

Give the charge each atom takes as soon as it develops an ion. If more than one charge is possible, list both.

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Ag Au Br

Give the charge each atom takes once it creates an ion. If more than one charge is feasible, list both.