Which Element Can Form More Than One Kind of Monatomic Ion?

Learning Objectives

1. Know how ions class.
2. Larn the characteristic charges that ions accept.
3. Construct a proper formula for an ionic chemical compound.
4. Generate a name for an ionic compound.

Then far, nosotros have discussed elements and compounds that are electrically neutral. They have the same number of electrons equally protons, so the negative charges of the electrons is balanced by the positive charges of the protons. However, this is not e'er the case. Electrons can move from i atom to another; when they do, species with overall electrical charges are formed. Such species are called ions. Species with overall positive charges are termed cations, while species with overall negative charges are called anions. Remember that ions are formed simply when electrons move from 1 atom to another; a proton never moves from one atom to another. Compounds formed from positive and negative ions are called ionic compounds.

Individual atoms can gain or lose electrons. When they do, they become monatomic ions. When atoms gain or lose electrons, they commonly proceeds or lose a characteristic number of electrons and then take on a feature overall accuse. Tabular array three.vi "Monatomic Ions of Various Charges" lists some common ions in terms of how many electrons they lose (making cations) or gain (making anions). At that place are several things to notice about the ions in Table 3.6 "Monatomic Ions of Various Charges". First, each element that forms cations is a metallic, except for i (hydrogen), while each element that forms anions is a nonmetal. This is really ane of the chemical properties of metals and nonmetals: metals tend to grade cations, while nonmetals tend to form anions. Second, most atoms course ions of a single characteristic charge. When sodium atoms form ions, they always form a 1+ accuse, never a two+ or 3+ or even one− charge. Thus, if you commit the data in Table iii.vi "Monatomic Ions of Various Charges" to memory, you volition always know what charges most atoms form. (In Chapter 9 "Chemical Bonds", nosotros volition discuss why atoms form the charges they practice.)

Table 3.half-dozen Monatomic Ions of Various Charges

Ions formed by losing a single electron	H+
	Na+
	K+
	Rb+
	Ag+
	Au+
Ions formed by losing two electrons	Mg2+
	Ca2+
	Sr2+
	Fe2+
	Coii+
	Niii+
	Cu2+
	Zn2+
	Sn2+
	Hgii+
	Pb2+
Ions formed past losing 3 electrons	Sc3+
	Iron3+
	Cothree+
	Ni3+
	Authree+
	Al3+
	Cr3+
Ions formed by losing 4 electrons	Tiiv+
	Sn4+
	Atomic number 824+
Ions formed by gaining a single electron	F−
	Cl−
	Br−
	I−
Ions formed past gaining ii electrons	O2−
	Due southtwo−
	Se2−
Ions formed past gaining three electrons	North3−
	Piii−

3rd, in that location are some exceptions to the previous indicate. A few elements, all metals, tin class more than i possible charge. For example, iron atoms can form 2+ cations or 3+ cations. Cobalt is another chemical element that tin can grade more than one possible charged ion (two+ and three+), while pb tin can class 2+ or 4+ cations. Unfortunately, there is little agreement which two charges a metallic cantlet may have, so it is all-time to just memorize the possible charges a particular element can accept.

Note the convention for indicating an ion. The magnitude of the accuse is listed as a right superscript next to the symbol of the element. If the accuse is a single positive or negative 1, the number 1 is not written; if the magnitude of the charge is greater than 1, then the number is written earlier the + or − sign. An chemical element symbol without a charge written adjacent to it is causeless to be the uncharged atom.

Naming an ion is straightforward. For a cation, merely use the name of the element and add the word ion (or if you want to be more than specific, add cation) after the chemical element's proper name. And then Na⁺ is the sodium ion; Ca^two+ is the calcium ion. If the element has more than one possible accuse, the value of the accuse comes afterward the element name and before the word ion. Thus, Atomic number 26²⁺ is the atomic number 26 two ion, while Atomic number 26³⁺ is the fe three ion. In print, we utilise roman numerals in parentheses to stand for the accuse on the ion, so these two atomic number 26 ions would be represented equally the atomic number 26(2) cation and the atomic number 26(3) cation, respectively.

For a monatomic anion, use the stem of the element proper noun and append the suffix -ide to information technology, and and so add ion. This is similar to how we named molecular compounds. Thus, Cl⁻ is the chloride ion, and N³⁻ is the nitride ion.

Example 6

Proper name each species.

1. O²⁻
2. Co
3. Co²⁺

Solution

1. This species has a 2− charge on it, and then it is an anion. Anions are named using the stem of the element proper name with the suffix -ide added. This is the oxide anion.
2. Because this species has no charge, it is an cantlet in its elemental form. This is cobalt.
3. In this case, in that location is a 2+ accuse on the atom, so it is a cation. We notation from Table 3.6 "Monatomic Ions of Various Charges" that cobalt cations can have ii possible charges, so the name of the ion must specify which accuse the ion has. This is the cobalt(II) cation.

Test Yourself

Name each species.

1. P³⁻
2. Sr^two+

Answers

1. the phosphide anion
2. the strontium cation

Chemical formulas for ionic compounds are chosen ionic formulas. A proper ionic formula has a cation and an anion in information technology; an ionic compound is never formed betwixt two cations but or ii anions only. The cardinal to writing proper ionic formulas is simple: the total positive charge must balance the full negative charge. Considering the charges on the ions are characteristic, sometimes we have to have more than than one of a cation or an anion to balance the overall positive and negative charges. Information technology is conventional to use the lowest ratio of ions that are needed to balance the charges.

For example, consider the ionic compound betwixt Na⁺ and Cl⁻. Each ion has a single charge, one positive and one negative, so nosotros need merely one ion of each to residue the overall charge. When writing the ionic formula, nosotros follow two additional conventions: (one) write the formula for the cation offset and the formula for the anion next, but (2) practise non write the charges on the ions. Thus, for the compound between Na⁺ and Cl⁻, we have the ionic formula NaCl (Figure 3.v "NaCl = Table Salt"). The formula Na_twoCl₂ also has balanced charges, but the convention is to use the lowest ratio of ions, which would be 1 of each. (Remember from our conventions for writing formulas that we don't write a 1 subscript if in that location is only one atom of a particular element present.) For the ionic chemical compound between magnesium cations (Mg²⁺) and oxide anions (O²⁻), again we need just 1 of each ion to residual the charges. Past convention, the formula is MgO.

Figure 3.5 NaCl = Tabular array Common salt

The ionic compound NaCl is very common.
Source: "Kosher Salt" past stlbites.com is licensed under the Artistic Eatables Attribution-NoDerivs 2.0 Generic.

For the ionic compound between Mg²⁺ ions and Cl⁻ ions, nosotros now consider the fact that the charges have dissimilar magnitudes, ii+ on the magnesium ion and 1− on the chloride ion. To balance the charges with the lowest number of ions possible, we need to have two chloride ions to balance the charge on the one magnesium ion. Rather than write the formula MgClCl, nosotros combine the two chloride ions and write it with a two subscript: MgCl₂.

What is the formula MgCl₂ telling usa? There are two chloride ions in the formula. Although chlorine as an element is a diatomic molecule, Cl_two, elemental chlorine is non office of this ionic compound. The chlorine is in the grade of a negatively charged ion, not the neutral chemical element. The two subscript is in the ionic formula because we demand two Cl⁻ ions to balance the accuse on i Mgⁱⁱ⁺ ion.

Case 7

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

1. Ca²⁺ and Cl⁻
2. Alⁱⁱⁱ⁺ and F⁻
3. Al³⁺ and O²⁻

Solution

1. We need two Cl⁻ ions to balance the accuse on one Ca²⁺ ion, and so the proper ionic formula is CaCl₂.
2. We demand three F⁻ ions to residue the charge on the Al³⁺ ion, and so the proper ionic formula is AlF₃.
3. With Al³⁺ and O²⁻, note that neither accuse is a perfect multiple of the other. This means we have to go to a least common multiple, which in this instance will be 6. To get a total of 6+, we need 2 Al^three+ ions; to get 6−, nosotros need three Oⁱⁱ⁻ ions. Hence the proper ionic formula is Al₂O_three.

Test Yourself

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

1. Fe²⁺ and Due south²⁻
2. Fe³⁺ and S²⁻

Answers

1. FeS
2. Fe₂S_three

Naming ionic compounds is simple: combine the name of the cation and the name of the anion, in both cases omitting the word ion. Do not use numerical prefixes if there is more than than one ion necessary to residuum the charges. NaCl is sodium chloride, a combination of the proper noun of the cation (sodium) and the anion (chloride). MgO is magnesium oxide. MgCl_ii is magnesium chloride—not magnesium dichloride.

In naming ionic compounds whose cations tin accept more than i possible charge, we must also include the charge, in parentheses and in roman numerals, as office of the name. Hence FeS is atomic number 26(Two) sulfide, while Atomic number 26₂South₃ is iron(3) sulfide. Once again, no numerical prefixes appear in the name. The number of ions in the formula is dictated past the need to balance the positive and negative charges.

Example 8

Name each ionic compound.

1. CaCl_ii
2. AlF₃
3. Co_twoO₃

Solution

1. Using the names of the ions, this ionic compound is named calcium chloride. Information technology is not calcium(II) chloride because calcium forms only one cation when it forms an ion, and information technology has a feature charge of ii+.
2. The proper name of this ionic compound is aluminum fluoride.
3. We know that cobalt can have more than than one possible charge; we just need to determine what it is. Oxide always has a two− charge, and so with three oxide ions, nosotros have a full negative charge of half-dozen−. This means that the two cobalt ions have to contribute half dozen+, which for 2 cobalt ions means that each ane is 3+. Therefore, the proper noun for this ionic compound is cobalt(III) oxide.

Test Yourself

Proper name each ionic chemical compound.

1. Sc₂O₃
2. AgCl

Answers

1. scandium oxide
2. silver chloride

How do you know whether a formula—and by extension, a name—is for a molecular compound or for an ionic compound? Molecular compounds form between nonmetals and nonmetals, while ionic compounds form between metals and nonmetals. The periodic tabular array (Figure 3.2 "A Simple Periodic Tabular array") tin be used to decide which elements are metals and nonmetals.

At that place also exists a grouping of ions that comprise more than than one atom. These are called polyatomic ions. Table three.7 "Common Polyatomic Ions" lists the formulas, charges, and names of some common polyatomic ions. Only one of them, the ammonium ion, is a cation; the rest are anions. Almost of them also incorporate oxygen atoms, and then sometimes they are referred to as oxyanions. Some of them, such as nitrate and nitrite, and sulfate and sulfite, have very similar formulas and names, then care must exist taken to get the formulas and names correct. Note that the -ite polyatomic ion has 1 less oxygen atom in its formula than the -ate ion but with the same ionic charge.

Tabular array 3.vii Mutual Polyatomic Ions

Name	Formula and Accuse		Name	Formula and Charge
ammonium	NH4 +		hydroxide	OH−
acetate	CiiH3O2 −, or CHiiiCOO−		nitrate	NO3 −
bicarbonate (hydrogen carbonate)	HCO3 −		nitrite	NO2 −
bisulfate (hydrogen sulfate)	HSO4 −		peroxide	O2 ii−
carbonate	COthree ii−		perchlorate	ClOiv −
chlorate	ClOthree −		phosphate	POfour 3−
chromate	CrOfour 2−		sulfate	SOfour 2−
cyanide	CN−		sulfite	SO3 ii−
dichromate	Cr2O7 2−		triiodide	I3 −

The naming of ionic compounds that contain polyatomic ions follows the aforementioned rules equally the naming for other ionic compounds: simply combine the name of the cation and the proper name of the anion. Do not use numerical prefixes in the name if there is more than one polyatomic ion; the only exception to this is if the name of the ion itself contains a numerical prefix, such as dichromate or triiodide.

Writing the formulas of ionic compounds has one important deviation. If more than than 1 polyatomic ion is needed to residue the overall charge in the formula, enclose the formula of the polyatomic ion in parentheses and write the proper numerical subscript to the right and outside the parentheses. Thus, the formula between calcium ions, Ca²⁺, and nitrate ions, NO_three ⁻, is properly written Ca(NO₃)_two, not CaNO₃₂ or Tin_iiO_vi. Use parentheses where required. The name of this ionic chemical compound is simply calcium nitrate.

Example 9

Write the proper formula and give the proper name for each ionic compound formed between the ii listed ions.

1. NH₄ ⁺ and S²⁻
2. Al³⁺ and PO₄ ³⁻
3. Atomic number 26²⁺ and PO₄ ^three−

Solution

1. Because the ammonium ion has a ane+ charge and the sulfide ion has a ii− charge, nosotros need two ammonium ions to balance the accuse on a unmarried sulfide ion. Enclosing the formula for the ammonium ion in parentheses, we have (NH₄)₂S. The compound's name is ammonium sulfide.
2. Because the ions have the aforementioned magnitude of charge, nosotros need merely ane of each to residue the charges. The formula is AlPO₄, and the name of the compound is aluminum phosphate.
3. Neither charge is an verbal multiple of the other, and then we have to get to the least common multiple of half-dozen. To go 6+, we need iii iron(II) ions, and to get 6−, nosotros demand 2 phosphate ions. The proper formula is Fe_iii(PO₄)₂, and the chemical compound's name is iron(II) phosphate.

Test Yourself

Write the proper formula and give the name for each ionic compound formed between the two listed ions.

1. NH₄ ⁺ and PO_iv ³⁻
2. Co^three+ and NO₂ ⁻

Answers

1. (NH₄)₃PO_four, ammonium phosphate
2. Co(NO₂)₃, cobalt(Iii) nitrite

Food and Drink App: Sodium in Your Food

The element sodium, at least in its ionic course every bit Na⁺, is a necessary nutrient for humans to live. In fact, the human being body is approximately 0.15% sodium, with the boilerplate person having ane-twentieth to i-tenth of a kilogram in their trunk at whatever given fourth dimension, generally in fluids outside cells and in other bodily fluids.

Sodium is likewise present in our diet. The common table salt we utilise on our foods is an ionic sodium compound. Many candy foods also contain significant amounts of sodium added to them equally a diversity of ionic compounds. Why are sodium compounds used then much? Ordinarily sodium compounds are inexpensive, simply, more importantly, well-nigh ionic sodium compounds dissolve easily. This allows processed nutrient manufacturers to add sodium-containing substances to nutrient mixtures and know that the chemical compound will dissolve 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 chosen sodium benzoate is added to many packaged foods equally a preservative. Table 3.8 "Some Sodium Compounds Added to Food" is a partial listing of some sodium additives used in food. Some of them you may recognize later reading this chapter. Others yous may not recognize, but they are all ionic sodium compounds with some negatively charged ion also present.

Table three.8 Some Sodium Compounds Added to Food

Sodium Compound	Apply in Food
Sodium acetate	preservative, acidity regulator
Sodium adipate	nutrient acrid
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	nutrient acid
Sodium dehydroacetate	preservative
Sodium erythorbate	antioxidant
Sodium erythorbin	antioxidant
Sodium ethyl para-hydroxybenzoate	preservative
Sodium ferrocyanide	anticaking amanuensis
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, colour fixative
Sodium nitrite	preservative, colour 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 fat acids	emulsifier, stabilizer, anticaking agent
Sodium sulfite	mineral common salt, preservative, antioxidant
Sodium sulfite	preservative, antioxidant
Sodium tartrate	food acid
Sodium tetraborate	preservative

The use of and so many sodium compounds in prepared and processed foods has alarmed some physicians and nutritionists. They argue that the boilerplate person consumes too much sodium from his or her diet. The average person needs only about 500 mg of sodium every day; almost people swallow more than this—upward to ten times equally much. Some studies have implicated increased sodium intake with high blood force per unit area; newer studies suggest that the link is questionable. However, there has been a push to reduce the amount of sodium most people ingest every solar day: avoid processed and manufactured foods, read labels on packaged foods (which include an indication of the sodium content), don't oversalt foods, and employ other herbs and spices too salt in cooking.

Nutrient labels include the amount of sodium per serving. This particular label shows that at that place are 75 mg of sodium in one serving of this particular food item.

Cardinal Takeaways

• Ions form when atoms lose or gain electrons.
• Ionic compounds have positive ions and negative ions.
• Ionic formulas balance the total positive and negative charges.
• Ionic compounds have a simple organisation of naming.
• Groups of atoms tin can accept an overall charge and make ionic compounds.

Exercises

1. Explain how cations form.

2. Explain how anions course.

3. Give the accuse each atom takes when information technology forms an ion. If more than than one accuse is possible, list both.

a)  M

b)  O

c)  Co

4.  Give the charge each cantlet takes when information technology forms an ion. If more than than one charge is possible, list both.

a)  Ca

b)  I

c)  Fe

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

a)  Ag

b)  Au

c)  Br

6.  Requite the accuse each atom takes when information technology forms an ion. If more than i charge is possible, list both.

a)  S

b)  Na

c)  H

vii.  Name the ions from Exercise three.

8.  Name the ions from Practise 4.

9  Proper name the ions from Do 5.

10.  Name the ions from Exercise half-dozen.

11.  Give the formula and name for each ionic compound formed between the two listed ions.

a)  Mg²⁺ and Cl⁻

b)  Fe²⁺ and O²⁻

c)  Atomic number 26³⁺ and O^two−

12.  Give the formula and name for each ionic compound formed between the ii listed ions.

a)  One thousand⁺ and Southward²⁻

b)  Ag⁺ and Br⁻

c)  Sr^two+ and Northward^three−

xiii.  Requite the formula and proper noun for each ionic compound formed between the two listed ions.

a)  Cu²⁺ and F⁻

b)  Ca²⁺ and O²⁻

c)  K⁺ and P³⁻

xiv.  Give the formula and name for each ionic compound formed between the two listed ions.

a)  Na⁺ and Northward³⁻

b)  Co²⁺ and I⁻

c)  Au³⁺ and S^two−

15.  Give the formula and proper name for each ionic compound formed betwixt the two listed ions.

a)  K⁺ and So_four ²⁻

b)  NH_iv ⁺ and S²⁻

c)  NH_iv ⁺ and PO₄ ³⁻

sixteen.  Give the formula and name for each ionic compound formed between the ii listed ions.

a)  Ca²⁺ and NO_iii ⁻

b)  Caⁱⁱ⁺ and NO₂ ⁻

c)  Sc^three+ and C₂H₃O_ii ⁻

17.  Give the formula and proper name for each ionic compound formed between the two listed ions.

a)  Pb⁴⁺ and And so_iv ²⁻

b)  Na⁺ and I₃ ⁻

c)  Li⁺ and Cr₂O₇ ²⁻

18.  Requite the formula and proper noun for each ionic chemical compound formed betwixt the two listed ions.

a)  NH₄ ⁺ and N^three−

b)  Mg²⁺ and CO₃ ²⁻

c)  Al³⁺ and OH⁻

19.  Give the formula and name for each ionic chemical compound formed betwixt the 2 listed ions.

a)  Ag⁺ and then₃ ²⁻

b)  Na⁺ and HCO_three ⁻

c)  Fe³⁺ and ClO₃ ⁻

20.  Give the formula and name for each ionic compound formed betwixt the ii listed ions.

a)  Rb⁺ and O₂ ²⁻

b)  Au^three+ and HSO_four ⁻

c)  Srⁱⁱ⁺ and NO_ii ⁻

21.  What is the difference between So₃ and Then₃ ²⁻?

22.  What is the departure between NO₂ and NO_ii ⁻?

Answers

1.

Cations form by losing electrons.

3.

a)  1+

b)  2−

c)  2+, 3+

5.

a)  i+

b)  1+, 3+

c)  1−

7.

a)  the potassium ion

b)  the oxide ion

c)  the cobalt(II) and cobalt(Three) ions, respectively

9.

a)  the silver ion

b)  the gold(I) and gold(III) ions, respectively

c)  the bromide ion

11.

a)  magnesium chloride, MgCl_two

b)  iron(II) oxide, FeO

c)  iron(III) oxide, Atomic number 26_twoO_three 13.

a)  copper(II) fluoride, CuF₂

b)  calcium oxide, CaO

c)  potassium phosphide, K₃P

xv.

a)  potassium sulfate, K_iiSO₄

b)  ammonium sulfide, (NH₄)₂South

c)  ammonium phosphate, (NH_four)₃PO₄ 17.

a)  lead(IV) sulfate, Pb(SO_four)_ii

b)  sodium triiodide, NaI₃

c)  lithium dichromate, Li₂Cr₂O_seven 19.

a)  silver sulfite, Ag₂And so₃

b)  sodium hydrogen carbonate, NaHCO_iii

c)  atomic number 26(III) chlorate, Fe(ClO₃)₃ 21.
SO_three is sulfur trioxide, while And then₃ ^two− is the sulfite ion.

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