Number Of Atoms In Silver

three.3: Predicting Charges of Ions

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Skills to Develop

Define ions, cations and anions
Predict the charge of an anion or cation based upon the location of the element in the periodic table

Ions of Elements

In ordinary chemic reactions, the nucleus of each atom remains unchanged. Electrons, notwithstanding, tin can exist added to atoms by transfer form other atoms, lost by transfer to other atoms, or shared with other atoms. The transfer and sharing of electrons amongst atoms govern the chemistry of the elements. During the formation of some compounds, atoms proceeds or lose electrons, and form electrically charged particles called ions (Figure \(\PageIndex{1}\); Video \(\PageIndex{1}\))

Figure A shows a sodium atom, N a, which has a nucleus containing 11 protons and 12 neutrons. The atom's surrounding electron cloud contains 11 electrons. Figure B shows a sodium ion, N a superscript plus sign. Its nucleus contains 11 protons and 12 neutrons. The ion's electron cloud contains 10 electrons and is smaller than that of the sodium atom in figure A.

Figure \(\PageIndex{1}\): (a) A sodium atom (Na) has equal numbers of protons and electrons (11) and is uncharged. (b) A sodium cation (Na⁺) has lost an electron, and so it has one more than proton (11) than electrons (10), giving it an overall positive charge, signified by a superscripted plus sign.

One tin can use the periodic tabular array to predict whether an atom will course an anion or a cation, and you can often predict the charge of the resulting ion. Atoms of many main-group metals lose plenty electrons to leave them with the same number of electrons equally an atom of the preceding noble gas. To illustrate, an atom of an alkali metal (grouping 1) loses i electron and forms a cation with a 1+ charge; an element of group ii (group 2) loses two electrons and forms a cation with a 2+ charge, and then on. For example, a neutral calcium atom, with twenty protons and twenty electrons, readily loses two electrons. This results in a cation with 20 protons, 18 electrons, and a two+ charge. It has the aforementioned number of electrons as atoms of the preceding noble gas, argon, and is symbolized Caⁱⁱ⁺. The proper name of a metal ion is the same every bit the name of the metal cantlet from which information technology forms, then Ca²⁺ is chosen a calcium ion.

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

Note the usefulness of the periodic tabular array in predicting likely ion formation and charge (Effigy \(\PageIndex{two}\)). Moving from the far left to the correct on the periodic table, primary-grouping elements tend to course cations with a charge equal to the grouping number. That is, group 1 elements form 1+ ions; group 2 elements form 2+ ions, and so on. Moving from the far right to the left on the periodic table, elements often class anions with a negative accuse equal to the number of groups moved left from the noble gases. For case, group 17 elements (one group left of the noble gases) grade 1− ions; group 16 elements (two groups left) form 2− ions, and and then on. This trend 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 another metals oft exhibit variable charges that are not predictable by their location in the tabular array. For example, copper can form ions with a i+ or 2+ accuse, and atomic number 26 can course ions with a 2+ or 3+ accuse.

Effigy \(\PageIndex{two}\): Some elements exhibit a regular design of ionic charge when they class ions.

Case \(\PageIndex{1}\): Limerick of Ions

An ion plant in some compounds used as antiperspirants contains 13 protons and 10 electrons. What is its symbol?

Solution

Because the number of protons remains unchanged when an atom forms an ion, the atomic number of the element must be 13. Knowing this lets us utilise the periodic table to place the element equally Al (aluminum). The Al cantlet has lost 3 electrons and thus has iii more than positive charges (13) than it has electrons (ten). This is the aluminum cation, Al^three+.

Exercise \(\PageIndex{ane}\)

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

Respond: Se²⁻, the selenide ion

Example \(\PageIndex{2}\): Formation of Ions

Magnesium and nitrogen 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 name them.

Solution

Magnesium's position in the periodic table (group 2) tells us that it is a metal. Metals form positive ions (cations). A magnesium cantlet must lose ii electrons to have the same number electrons as an atom of the previous noble gas, neon. Thus, a magnesium atom will form a cation with 2 fewer electrons than protons and a charge of 2+. The symbol for the ion is Mgⁱⁱ⁺, and it is called a magnesium ion.

Nitrogen's position in the periodic table (group 15) reveals that it is a nonmetal. Nonmetals form negative ions (anions). A nitrogen cantlet must gain three electrons to have the same number of electrons as an atom of the following noble gas, neon. Thus, a nitrogen cantlet will form an anion with 3 more electrons than protons and a charge of 3−. The symbol for the ion is Northⁱⁱⁱ⁻, and it is called a nitride ion.

Exercise \(\PageIndex{2}\)

Aluminum and carbon react to grade an ionic chemical 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.

Reply: Al volition form a cation with a charge of iii+: Al³⁺, an aluminum ion. Carbon volition form an anion with a charge of 4−: C^four−, a carbide ion.

Summary

Video \(\PageIndex{one}\): What are ions?

Glossary

anion: negative ions that are formed when a nonmental atom gains one or more electrons.
cation: positive ions that are formed when an atom loses electrons

ion: atom or molecule that has gained or lost one or more of its valence electrons, giving information technology a net electrical charge.


Contributors

Paul Flowers (University of N Carolina - Pembroke), Klaus Theopold (Academy of Delaware) and Richard Langley (Stephen F. Austin Country University) with contributing authors.Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at http://cnx.org/contents/85abf193-2bd...a7ac8df6@9.110).
Adelaide Clark, Oregon Institute of Technology
Fuse School, Open Educational Resources free of charge, under a Creative Commons License: Attribution-NonCommercial CC BY-NC (View License Human activity: https://creativecommons.org/licenses/past-nc/4.0/)