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

In ordinary chemical reactions, the cell core of each atom (and for this reason the identity of the element) stays unchanged. Electrons, however, can be added to atom by transport from various other atoms, lost by transfer to various other atoms, or mutual with various other atoms. The transfer and sharing of electrons among atoms govern the chemistry that the elements. During the formation of some compounds, atoms obtain or lose electrons, and form electrically charged particles called ions ().

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Some facets exhibit a continuous pattern of ionic charge once they type ions.


Composition that IonsAn ion discovered in part compounds supplied as antiperspirants consists of 13 protons and also 10 electrons. What is its symbol?

SolutionBecause the variety of protons stays unchanged as soon as an atom forms an ion, the atomic variety of the aspect must be 13. Understanding this lets us use the periodic table to identify the facet as Al (aluminum). The Al atom has lost 3 electrons and thus has actually three an ext positive charges (13) 보다 it has actually electrons (10). This is the aluminum cation, Al3+.

Check her LearningGive the symbol and name for the ion through 34 protons and also 36 electrons.


Formation that IonsMagnesium and nitrogen react to kind an ionic compound. Predict which creates an anion, which develops a cation, and the fees of every ion. Compose the symbol because that each ion and name them.

SolutionMagnesium’s position in the routine table (group 2) tells us that the is a metal. Metals type positive ions (cations). A magnesium atom must shed two electron to have actually the very same number electrons together an atom the the previous noble gas, neon. Thus, a magnesium atom will type a cation v two under electrons than protons and also a charge of 2+. The symbol because that the ion is Mg2+, and also it is called a magnesium ion.

Nitrogen’s position in the regular table (group 15) reveals the it is a nonmetal. Nonmetals type negative ion (anions). A nitrogen atom must get three electrons to have the same number of electrons as an atom that the adhering to noble gas, neon. Thus, a nitrogen atom will type an anion v three an ext electrons 보다 protons and also a fee of 3−. The symbol because that the ion is N3−, and it is referred to as a nitride ion.

Check her LearningAluminum and carbon react to kind an ionic compound. Predict which creates an anion, which develops a cation, and the dues of each ion. Create the symbol because that each ion and also name them.


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


The ion that us have disputed so much are called monatomic ions, that is, they room ions created from just one atom. We additionally find many polyatomic ions. This ions, i beg your pardon act as discrete units, are electrically charged molecules (a group of external inspection atoms v an all at once charge). Several of the more important polyatomic ions are listed in . Oxyanions room polyatomic ions that contain one or much more oxygen atoms. At this point in your examine of chemistry, you should memorize the names, formulas, and charges of the most common polyatomic ions. Due to the fact that you will usage them repeatedly, they will soon end up being familiar.

Common Polyatomic IonsNameFormulaRelated AcidFormula
ammonium( extNH_4^+)
hydronium( extH_3 extO^+)
oxide( extO^2-)
peroxide( extO_2^2-)
hydroxide( extOH^-)
acetate( extCH_3 extCOO^-)acetic acidCH3COOH
cyanideCN−hydrocyanic acidHCN
azide( extN_3^-)hydrazoic acidHN3
carbonate( extCO_3^2-)carbonic acidH2CO3
bicarbonate( extHCO_3^-)
nitrate( extNO_3^-)nitric acidHNO3
nitrite( extNO_2^-)nitrous acidHNO2
sulfate( extSO_4^2-)sulfiric acidH2SO4
hydrogen sulfate( extHSO_4^-)
sulfite( extSO_3^2-)sulfurous acidH2SO3
hydrogen sulfite( extHSO_3^-)
phosphate( extPO_4^3-)phosphoric acidH3PO4
hydrogen phosphate( extHPO_4^2-)
dihydrogen phosphate( extH_2 extPO_4^-)
perchlorate( extClO_4^-)perchloric acidHClO4
chlorate( extClO_3^-)chloric acidHClO3
chlorite( extClO_2^-)chlorous acidHClO2
hypochloriteClO−hypochlorous acidHClO
chromate( extCrO_4^2-)chromic acidH2Cr2O4
dichromate( extCr_2 extO_7^2-)dichromic acidH2Cr2O7
permanganate( extMnO_4^-)permanganic acidHMnO4

Note that there is a mechanism for naming some polyatomic ions; -ate and also -ite space suffixes designating polyatomic ions containing an ext or fewer oxygen atoms. Per- (short for “hyper”) and also hypo- (meaning “under”) room prefixes an interpretation more oxygen atoms than -ate and fewer oxygen atoms 보다 -ite, respectively. For example, perchlorate is ( extClO_4^- ext,) chlorate is ( extClO_3^- ext,) chlorite is ( extClO_2^-) and hypochlorite is ClO−. Unfortunately, the variety of oxygen atoms equivalent to a given suffix or prefix is no consistent; for example, nitrate is ( extNO_3^-) when sulfate is ( extSO_4^2-.) This will be spanned in an ext detail in the following module top top nomenclature.

The nature the the attractive pressures that host atoms or ions with each other within a compound is the basis for classifying chemical bonding. When electrons are transferred and also ions form, ionic bond result. Ionic bonds space electrostatic pressures of attraction, that is, the attractive forces experienced in between objects that opposite electrical charge (in this case, cations and anions). As soon as electrons are “shared” and also molecules form, covalent binding result. Covalent bonds space the attractive forces in between the positively fee nuclei that the external inspection atoms and one or much more pairs of electron that are located between the atoms. Compounds room classified as ionic or molecule (covalent) on the communication of the bonds present in them.


Ionic Compounds

When an aspect composed that atoms that readily lose electrons (a metal) reacts with an facet composed of atoms the readily get electrons (a nonmetal), a transport of electrons commonly occurs, developing ions. The compound developed by this carry is stabilized by the electrostatic attractions (ionic bonds) in between the ion of the contrary charge present in the compound. Because that example, when each sodium atom in a sample that sodium steel (group 1) offers up one electron to type a salt cation, Na+, and each chlorine atom in a sample of chlorine gas (group 17) accepts one electron to kind a chloride anion, Cl−, the resulting compound, NaCl, is composed of sodium ions and also chloride ions in the proportion of one Na+ ion for each Cl− ion. Similarly, each calcium atom (group 2) can give up 2 electrons and also transfer one to each of two chlorine atoms to kind CaCl2, i beg your pardon is composed of Ca2+ and also Cl− ions in the ratio of one Ca2+ ion to 2 Cl− ions.

A link that consists of ions and also is hosted together by ionic bond is dubbed an ionic compound. The periodic table can help us recognize countless of the compound that space ionic: as soon as a steel is an unified with one or much more nonmetals, the compound is generally ionic. This tip works well because that predicting ionic compound formation for most of the compounds typically encountered in an introductory chemistry course. However, it is not constantly true (for example, aluminum chloride, AlCl3, is no ionic).

You can often recognize ionic compounds due to the fact that of their properties. Ionic compounds are solids that generally melt at high temperatures and boil at even greater temperatures. For example, salt chloride melts in ~ 801 °C and boils at 1413 °C. (As a comparison, the molecular link water melts in ~ 0 °C and boils at 100 °C.) In solid form, one ionic link is not electrically conductive because its ions are unable to flow (“electricity” is the flow of charged particles). As soon as molten, however, it deserve to conduct electricity because its ions space able to move easily through the liquid ().


Watch this video clip to watch a mixture of salt melt and also conduct electricity.


In every ionic compound, the total variety of positive dues of the cations equals the complete number of an adverse charges that the anions. Thus, ionic compounds are electrically neutral overall, also though they contain hopeful and an unfavorable ions. We have the right to use this observation to help us write the formula of an ionic compound. The formula of an ionic link must have actually a ratio of ion such the the numbers of optimistic and negative charges are equal.


Predicting the Formula of one Ionic CompoundThe gemstone sapphire () is largely a link of aluminum and oxygen that has aluminum cations, Al3+, and oxygen anions, O2−. What is the formula of this compound?


Although pure aluminum oxide is colorless, trace quantities of iron and also titanium give blue sapphire its characteristic color. (credit: change of job-related by Stanislav Doronenko)


SolutionBecause the ionic compound have to be electrically neutral, it must have actually the same number of positive and an adverse charges. Two aluminum ions, each through a fee of 3+, would offer us six optimistic charges, and three oxide ions, each through a fee of 2−, would provide us six an unfavorable charges. The formula would certainly be Al2O3.

Check her LearningPredict the formula of the ionic link formed between the sodium cation, Na+, and the sulfide anion, S2−.


Many ionic compounds save on computer polyatomic ions () together the cation, the anion, or both. As with straightforward ionic compounds, these compounds must additionally be electrically neutral, so their formulas deserve to be guess by treating the polyatomic ion as discrete units. We usage parentheses in a formula to indicate a team of atoms the behave as a unit. Because that example, the formula for calcium phosphate, among the minerals in ours bones, is Ca3(PO4)2. This formula suggests that there space three calcium ion (Ca2+) for every 2 phosphate (left( extPO_4^3- ight)) groups. The ( extPO_4^3-) groups are discrete units, every consisting that one phosphorus atom and also four oxygen atoms, and having an as whole charge that 3−. The compound is electrically neutral, and also its formula reflects a complete count of 3 Ca, two P, and eight O atoms.


Predicting the Formula the a Compound through a Polyatomic AnionBaking powder consists of calcium dihydrogen phosphate, an ionic compound written of the ions Ca2+ and also ( extH_2 extPO_4^-.) What is the formula of this compound?

SolutionThe hopeful and an unfavorable charges must balance, and also this ionic compound should be electrically neutral. Thus, us must have actually two an unfavorable charges come balance the 2+ charge of the calcium ion. This needs a proportion of one Ca2+ ion to 2 ( extH_2 extPO_4^-) ions. Us designate this through enclosing the formula for the dihydrogen phosphate ion in parentheses and adding a subscript 2. The formula is Ca(H2PO4)2.

Check your LearningPredict the formula that the ionic link formed in between the lithium ion and the peroxide ion, ( extO_2^2-) (Hint: usage the routine table to predict the sign and also the charge on the lithium ion.)


Because one ionic compound is not comprised of single, discrete molecules, it may not be properly symbolized making use of a molecular formula. Instead, ionic compounds need to be symbolized through a formula denote the relative numbers that its constituent ions. For compounds containing only monatomic ion (such as NaCl) and for many compounds comprise polyatomic ions (such as CaSO4), these formulas are just the empirical formulas introduced earlier in this chapter. However, the recipe for some ionic compounds containing polyatomic ions space not empirical formulas. For example, the ionic compound sodium oxalate is comprised of Na+ and ( extC_2 extO_4^2-) ions merged in a 2:1 ratio, and also its formula is created as Na2C2O4. The subscripts in this formula room not the smallest-possible whole numbers, as each have the right to be split by 2 to yield the empirical formula, NaCO2. This is not the accepted formula for sodium oxalate, however, as it does no accurately stand for the compound’s polyatomic anion, ( extC_2 extO_4^2-.)


Molecular Compounds

Many compounds carry out not contain ions however instead consist specifically of discrete, neutral molecules. This molecular compounds (covalent compounds) result when atoms share, fairly than move (gain or lose), electrons. Covalent bonding is crucial and extensive principle in chemistry, and it will be treated in significant detail in a later on chapter of this text. Us can often identify molecule compounds ~ above the basis of their physical properties. Under regular conditions, molecular compounds regularly exist as gases, low-boiling liquids, and also low-melting solids, although numerous important exception exist.

Whereas ionic compounds are usually developed when a metal and also a nonmetal combine, covalent compounds room usually developed by a combination of nonmetals. Thus, the periodic table can help us recognize numerous of the compound that room covalent. While we have the right to use the location of a compound’s facets in the routine table to predict even if it is it is ionic or covalent at this suggest in our study of chemistry, you have to be mindful that this is a an extremely simplistic technique that does no account for a variety of interesting exceptions. Shades the gray exist between ionic and molecular compounds, and also you’ll learn more about those later.


Predicting the form of Bonding in CompoundsPredict even if it is the following compounds room ionic or molecular:

(a) KI, the compound used as a resource of iodine in table salt

(b) H2O2, the bleach and disinfectant hydrogen peroxide

(c) CHCl3, the anesthetic chloroform

(d) Li2CO3, a resource of lithium in antidepressants

Solution(a) Potassium (group 1) is a metal, and also iodine (group 17) is a nonmetal; KI is suspect to it is in ionic.

(b) Hydrogen (group 1) is a nonmetal, and oxygen (group 16) is a nonmetal; H2O2 is guess to it is in molecular.

(c) Carbon (group 14) is a nonmetal, hydrogen (group 1) is a nonmetal, and chlorine (group 17) is a nonmetal; CHCl3 is guess to be molecular.

(d) Lithium (group 1) is a metal, and carbonate is a polyatomic ion; Li2CO3 is guess to it is in ionic.

Check her LearningUsing the periodic table, predict whether the following compounds are ionic or covalent:

(a) SO2

(b) CaF2

(c) N2H4

(d) Al2(SO4)3


Key Concepts and Summary

Metals (particularly those in groups 1 and 2) have tendency to shed the variety of electrons that would leave them through the same number of electrons together in the preceding noble gas in the periodic table. Through 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 obtain the number of electrons needed to administer atoms through the same number of electrons together in the next noble gas in the periodic table. Thus, nonmetals have tendency to kind negative ions. Positively charged ion are referred to as cations, and also negatively charged ion are referred to as anions. Ions can be one of two people monatomic (containing just one atom) or polyatomic (containing more than one atom).

Compounds that contain ion are dubbed ionic compounds. Ionic compound generally form from metals and also nonmetals. Compound that do not contain ions, yet instead consists of atoms bonded tightly with each other in molecules (uncharged teams of atoms the behave as a solitary unit), are dubbed covalent compounds. Covalent compound usually type from two nonmetals.


Using the regular table, predict even if it is the adhering to chlorides space ionic or covalent: KCl, NCl3, ICl, MgCl2, PCl5, and also CCl4.

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Using the regular table, predict even if it is the following chlorides room ionic or covalent: SiCl4, PCl3, CaCl2, CsCl, CuCl2, and CrCl3.


For each of the complying with compounds, state even if it is it is ionic or covalent. If it is ionic, compose the icons for the ion involved:

(a) NF3

(b) BaO,

(c) (NH4)2CO3

(d) Sr(H2PO4)2

(e) IBr

(f) Na2O


(a) covalent; (b) ionic, Ba2+, O2−; (c) ionic, ( extNH_4^+ ext,) ( extCO_3^2-;) (d) ionic, Sr2+, ( extH_2 extPO_4^-;) (e) covalent; (f) ionic, Na+, O2−


For every of the following compounds, state whether it is ionic or covalent, and also if it is ionic, write the icons for the ion involved:

(a) KClO4

(b) Mg(C2H3O2)2

(c) H2S

(d) Ag2S

(e) N2Cl4

(f) Co(NO3)2


For each of the adhering to pairs that ions, compose the symbol because that the formula of the link they will certainly form:

(a) Ca2+, S2−

(b) ( extNH_4^+ ext,) ( extSO_4^2-)

(c) Al3+, Br−

(d) Na+, ( extHPO_4^2-)

(e) Mg2+, ( extPO_4^3-)


For every of the following pairs that ions, write the symbol because that the formula the the compound they will form:

(a) K+, O2−

(b) ( extNH_4^+ ext,) ( extPO_4^3-)

(c) Al3+, O2−

(d) Na+, ( extCO_3^2-)

(e) Ba2+, ( extPO_4^3-)


Glossary

covalent bondattractive force between the nuclei that a molecule’s atoms and also pairs that electrons between the atomscovalent compound(also, molecular compound) composed of molecules formed by atom of 2 or much more different elementsionic bondelectrostatic pressures of attraction between the oppositely charged ion of one ionic compoundionic compoundcompound written of cations and anions linked in ratios, yielding one electrically neutral substancemolecular compound(also, covalent compound) created of molecules developed by atoms of two or much more different elementsmonatomic ionion created of a solitary atomoxyanionpolyatomic anion created of a main atom external inspection to oxygen atomspolyatomic ionion created of more than one atom