metals tend to form what kind of ions

Learning Objectives

By the stop of this section, you will be able to:

• Define ionic and molecular (covalent) compounds
• Predict the type of chemical compound formed from elements based on their location within the periodic table

In ordinary chemical reactions, the nucleus of each atom (and thus the identity of the element) remains unchanged. Electrons, however, can be added to atoms past transfer from other atoms, lost past transfer to other atoms, or shared with other atoms. The transfer and sharing of electrons among atoms govern the chemistry of the elements. During the germination of some compounds, atoms gain or lose electrons, and form electrically charged particles called ions (Figure 1).

Figure 1. (a) A sodium atom (Na) has equal numbers of protons and electrons (xi) and is uncharged. (b) A sodium cation (Na+) has lost an electron, so it has one more proton (eleven) than electrons (ten), giving it an overall positive charge, signified by a superscripted plus sign.

You lot can use the periodic table to predict whether an cantlet will grade an anion or a cation, and yous can oftentimes predict the charge of the resulting ion. Atoms of many master-group metals lose enough electrons to leave them with the same number of electrons as an atom of the preceding noble gas. To illustrate, an atom of an alkali metal (group 1) loses one electron and forms a cation with a 1+ charge; an alkaline metal earth metal (grouping 2) loses two electrons and forms a cation with a 2+ charge, and so on. For example, a neutral calcium cantlet, with xx protons and 20 electrons, readily loses two electrons. This results in a cation with 20 protons, 18 electrons, and a two+ charge. It has the same number of electrons equally atoms of the preceding noble gas, argon, and is symbolized Ca^two+. The proper name of a metal ion is the same as the name of the metallic atom from which information technology forms, then Ca²⁺ is called a calcium ion.

When atoms of nonmetal elements class ions, they generally gain enough electrons to give them the aforementioned number of electrons as an atom of the next noble gas in the periodic table. Atoms of group 17 gain 1 electron and form anions with a one− accuse; atoms of grouping 16 proceeds two electrons and form ions with a 2− charge, and so on. For instance, the neutral bromine atom, with 35 protons and 35 electrons, can proceeds one electron to provide it with 36 electrons. This results in an anion with 35 protons, 36 electrons, and a i− accuse. It has the aforementioned number of electrons as atoms of the side by side noble gas, krypton, and is symbolized Br⁻. (A discussion of the theory supporting the favored condition of noble gas electron numbers reflected in these predictive rules for ion formation is provided in a afterwards affiliate of this text.)

Note the usefulness of the periodic tabular array in predicting likely ion formation and charge (Figure 2). Moving from the far left to the right on the periodic tabular array, main-group elements tend to form cations with a charge equal to the group number. That is, grouping 1 elements course 1+ ions; group 2 elements form two+ ions, and so on. Moving from the far correct to the left on the periodic table, elements ofttimes form anions with a negative charge equal to the number of groups moved left from the noble gases. For example, group 17 elements (one group left of the noble gases) form 1− ions; grouping 16 elements (two groups left) form 2− ions, and so on. This tendency tin can be used as a guide in many cases, but its predictive value decreases when moving toward the center of the periodic table. In fact, transition metals and some other metals often exhibit variable charges that are not anticipated past their location in the table. For instance, copper tin grade ions with a i+ or 2+ accuse, and iron can form ions with a 2+ or 3+ accuse.

Figure two. Some elements showroom a regular pattern of ionic accuse when they form ions.

Example ane: Composition of Ions

An ion constitute in some compounds used as antiperspirants contains 13 protons and x electrons. What is its symbol?

Show Answer

Because the number of protons remains unchanged when an atom forms an ion, the atomic number of the element must exist 13. Knowing this lets us apply the periodic table to identify the element every bit Al (aluminum). The Al atom has lost 3 electrons and thus has three more than positive charges (xiii) than information technology has electrons (10). This is the aluminum cation, Al³⁺.

Cheque Your Learning

Give the symbol and name for the ion with 34 protons and 36 electrons.

Prove Reply

Se²⁻, the selenide ion

Example 2: Germination of Ions

Magnesium and nitrogen react to class an ionic compound. Predict which forms an anion, which forms a cation, and the charges of each ion. Write the symbol for each ion and name them.

Bank check Your Learning

Aluminum and carbon react to form an ionic compound. Predict which forms an anion, which forms a cation, and the charges of each ion. Write the symbol for each ion and proper noun them.

Prove Answer

Al will course a cation with a charge of three+: Al³⁺, an aluminum ion. Carbon volition form an anion with a charge of iv−: C^iv−, a carbide ion.

The nature of the attractive forces that hold atoms or ions together within a compound is the basis for classifying chemic bonding. When electrons are transferred and ions form, ionic bonds result. Ionic bonds are electrostatic forces of attraction, that is, the bonny forces experienced between objects of opposite electrical charge (in this example, cations and anions). When electrons are "shared" and molecules form, covalent bonds consequence. Covalent bonds are the attractive forces between the positively charged nuclei of the bonded atoms and one or more pairs of electrons that are located between the atoms. Compounds are classified as ionic or molecular (covalent) on the ground of the bonds present in them.

Ionic Compounds

When an element equanimous of atoms that readily lose electrons (a metal) reacts with an element composed of atoms that readily gain electrons (a nonmetal), a transfer of electrons usually occurs, producing ions. The compound formed by this transfer is stabilized by the electrostatic attractions (ionic bonds) between the ions of opposite charge present in the compound. For example, when each sodium atom in a sample of sodium metal (grouping 1) gives upwardly one electron to form a sodium cation, Na⁺, and each chlorine atom in a sample of chlorine gas (grouping 17) accepts i electron to form a chloride anion, Cl⁻, the resulting compound, NaCl, is composed of sodium ions and chloride ions in the ratio of one Na⁺ ion for each Cl⁻ ion. Similarly, each calcium atom (group ii) tin can give upwards two electrons and transfer one to each of two chlorine atoms to course CaCl₂, which is composed of Caⁱⁱ⁺ and Cl⁻ ions in the ratio of one Ca²⁺ ion to two Cl⁻ ions.

A compound that contains ions and is held together by ionic bonds is called an ionic compound. The periodic table can help us recognize many of the compounds that are ionic: When a metal is combined with one or more nonmetals, the compound is usually ionic. This guideline works well for predicting ionic compound formation for nigh of the compounds typically encountered in an introductory chemistry form. However, information technology is not always true (for example, aluminum chloride, AlCl₃, is not ionic).

You can oftentimes recognize ionic compounds because of their backdrop. Ionic compounds are solids that typically melt at high temperatures and boil at fifty-fifty higher temperatures. For case, sodium chloride melts at 801 °C and boils at 1413 °C. (As a comparison, the molecular compound h2o melts at 0 °C and boils at 100 °C.) In solid form, an ionic compound is not electrically conductive because its ions are unable to flow ("electricity" is the flow of charged particles). When molten, however, it tin can carry electricity considering its ions are able to move freely through the liquid (Figure 3).

Figure three. Sodium chloride melts at 801 °C and conducts electricity when molten. (credit: modification of work by Marking Blaser and Matt Evans)

Watch this video to run across a mixture of salts cook and bear electricity.

Molecular Compounds

Many compounds do non contain ions just instead consist solely of detached, neutral molecules. These molecular compounds (covalent compounds) consequence when atoms share, rather than transfer (gain or lose), electrons. Covalent bonding is an of import and extensive concept in chemistry, and information technology will exist treated in considerable detail in a afterwards chapter of this text. We tin often identify molecular compounds on the basis of their physical properties. Under normal weather condition, molecular compounds oft exist as gases, low-boiling liquids, and low-melting solids, although many important exceptions exist.

Whereas ionic compounds are usually formed when a metal and a nonmetal combine, covalent compounds are usually formed by a combination of nonmetals. Thus, the periodic table tin aid u.s.a. recognize many of the compounds that are covalent. While we tin can employ the positions of a chemical compound's elements in the periodic table to predict whether it is ionic or covalent at this bespeak in our report of chemical science, you should be enlightened that this is a very simplistic approach that does not account for a number of interesting exceptions. Shades of grayness exist between ionic and molecular compounds, and y'all'll learn more about those after.

Case 5: Predicting the Type of Bonding in Compounds

Predict whether the following compounds are ionic or molecular:

1. KI, the chemical compound used equally a source of iodine in salt
2. H₂O_ii, the bleach and disinfectant hydrogen peroxide
3. CHCl₃, the anesthetic chloroform
4. Li₂CO_three, a source of lithium in antidepressants

Bank check Your Learning

Using the periodic tabular array, predict whether the following compounds are ionic or covalent:

1. SO_two
2. CaF_two
3. N_twoH_four
4. Al₂(SO₄)₃

Key Concepts and Summary

Metals (particularly those in groups ane and 2) tend to lose the number of electrons that would get out them with the same number of electrons as in the preceding noble gas in the periodic table. By this means, a positively charged ion is formed. Similarly, nonmetals (especially those in groups 16 and 17, and, to a lesser extent, those in Group 15) can gain the number of electrons needed to provide atoms with the same number of electrons as in the side by side noble gas in the periodic tabular array. Thus, nonmetals tend to form negative ions. Positively charged ions are called cations, and negatively accuse ions are called anions. Ions tin can be either monatomic (containing only one atom) or polyatomic (containing more than one atom).

Compounds that contain ions are called ionic compounds. Ionic compounds generally class from metals and nonmetals. Compounds that practice not comprise ions, but instead consist of atoms bonded tightly together in molecules (uncharged groups of atoms that behave equally a single unit), are called covalent compounds. Covalent compounds usually form from two nonmetals.

Exercises

1. Using the periodic table, predict whether the following chlorides are ionic or covalent: KCl, NCl_three, ICl, MgCl_ii, PCl₅, and CCl₄.
2. Using the periodic tabular array, predict whether the following chlorides are ionic or covalent: SiCl_iv, PCl₃, CaCl_two, CsCl, CuCl_ii, and CrCl₃.
3. For each of the following compounds, state whether it is ionic or covalent. If it is ionic, write the symbols for the ions involved:
   1. NF₃
   2. BaO,
   3. (NH₄)₂CO_three
   4. Sr(H₂PO₄)₂
   5. IBr
   6. Na₂O
4. For each of the following compounds, country whether information technology is ionic or covalent, and if it is ionic, write the symbols for the ions involved:
   1. KClO_four
   2. MgC₂H₃O_ii
   3. H₂S
   4. Ag_iiS
   5. North₂Cl_iv
   6. Co(NO_three)₂

Glossary

covalent bail: attractive force between the nuclei of a molecule'southward atoms and pairs of electrons betwixt the atoms

covalent compound: (also, molecular compound) composed of molecules formed by atoms of 2 or more different elements

ionic bond: electrostatic forces of attraction betwixt the oppositely charged ions of an ionic chemical compound

ionic compound: compound composed of cations and anions combined in ratios, yielding an electrically neutral substance

molecular compound: (also, covalent compound) composed of molecules formed by atoms of two or more than different elements

monatomic ion: ion equanimous of a unmarried cantlet

lombardibothe1936.blogspot.com

Source: https://courses.lumenlearning.com/suny-mcc-introductorychemistry/chapter/ions-and-ionic-compounds/

Share this post