ATOMIC ORBITAL DIAGRAMS AND ELECTRON CONFIGURATION.

ATOMIC ORBITAL DIAGRAMS

AND

ELECTRON CONFIGURATION

ATOMIC ORBITAL DIAGRAMS

AND

ELECTRON CONFIGURATION

CHEMICAL BONDS, MOLECULES, AND COMPOUNDS

Lewis Dot Symbols Show Valence Electrons

- Nobel Gas Electron Configuration – Octet Rule

The Octet Rule for Some Diatomic Gases (H2, N2, O2, F2)

Example of F2

•Single covalent bond consisting of 2 shared electrons

•By sharing, each F gets a stable octet of 8 electrons

•Same as neon, the noble gas immediately following F

(4.2.1)

The Octet Rule for Chemical Compounds• Atoms attempt to attain a noble gas electron configuration in

compounds

Figure 4.3. Stable EC of noble gas in the ionic compound NaCl acquired when the Na atom loses an electron and the Cl atom gains an electron

Carbon tends to share electrons to form covalent bonds with almost all other elements as shown for methane gas in Figure 4.4

IONIC BONDING• An ion is an atom or group of atoms having an unequal number of electrons and protons, therefore, a net electrical charge

• Cation has a positive charge • Anion has a negative charge

• The most stable cations and anions have the same number of electrons as a noble gas – They are isoelectronic to a noble gas.

An ionic compound contains both cations and anions

• Held together by ionic bonds

Table 4.1. Ions with Neon and Argon Electron Configurations

Electron Electrons Ion electronElement configuration gained/lost Ion configuration

Isoelectronic with noble gas EC

Figure 4.5. Representation of the Structure of Ionic NaCl

Nearest ions to each Cl- ion (arrow) are 6 Na+ ions and nearest ions to each

Na+ ion are 6 Cl- ions

Lattice Energy• Lattice energy is the energy required to separate all the ions in a

crystalline lattice

• The lattice energy of NaCl is +785 kJ/mol

Ion Size• Smaller ions get closer increasing lattice energy

• Cations smaller than corresponding neutral atoms

• Anions are larger than corresponding neutral atoms

• Cations decrease in size across a period with increasing + charge

• Anions increase in size across a period with increasing - charge

• See trends in ion size in Figure 4.7

Relative Diameters of Some Ions from Single Atoms

Diameters in picometers, pm

Formation of Some Example Ionic Compounds

Al2O3

CHEMICAL FORMULAS OF COMPOUNDSFigure 4.16. Example of Calcium Phosphate

CHEMICAL FORMULAS OF IONIC COMPOUNDS

CHEMICAL FORMULAS OF IONIC COMPOUNDS

Naming Cations

• Elements of Groups 1A, 2A, and Al form only one type of cation; the name of the cation is the name of the metal followed by the word “ion” “Always ions”

Li+H+ Hydrogen ion

Lithium ion

Sodium ionPotassium ion

Ion

K+

Na+

Mg2+ Magnesium ion

Calcium ion

Strontium ionBarium ion

Ca2+

Sr2+

Ba2+

Al3+ Aluminum ion

Name Ion Name Ion Name

Group 1A Group 2A Group 3A

Naming Cations

• For cations derived from other metals, – use Roman numerals to show charge

Example:

Iron(II) is Fe2+

Iron (III) is Fe3+

Naming Cations

• For cations derived from other metals, – use Roman numerals to show charge

Example:

Iron(II) is Fe2+

Iron (III) is Fe3+

Naming Cations

Fe3+

Fe2+

Hg+

Hg2+

Cu2+

Cu+ Copper(I) ionCopper(II) ion

Iron(II) ionIron(III) ion

Mercury(I) ionMercury(II) ion

Cuprous ionCupric ion

Ferrous ionFerric ion

Mercurous ionMercuric ion

Cupr- from cuprum, the Latinname for copper

Hg from hydrargyrum, theLatin name for mercury

IonSystematic name

Common name

Origin of the symbol of theelement or the common name of the ion

Ferr- from ferrum, the Latinname for iron

Sn2+

Sn4+

Tin(II) ionTin(IV) ion

Stannous ionStannic ion

Sn from stannum, theLatin name for tin

Do

No

t Use

Naming Anions

• For monatomic (containing only one atom) anions, add “ide” to the end– here are the monatomic anions we deal with most

often

Anion

F-

Cl-

Br-

I-

O2-

S2-

Stemname

fluorchlorbromiodoxsulf

Anionname

fluoridechloridebromideiodideoxidesulfide

Polyatomic Ions

– common names, where still widely used, are given in parentheses

NH4+

OH-

NO2-

NO3-

CH3COO-

CN-

MnO4-

CO32-

HCO3-

SO32-

HSO3-

SO42-

PO43-

HPO32-

H2PO4-

HSO4-

CrO42-

Ammonium

HydroxideNitrite

NitrateAcetate

Cyanide

Permanganate

Carbonate

Hydrogen carbonate (Bicarbonate)

IonName

SulfiteHydrogen sulfite (Bisulfite)

Sulfate

Phosphate

Hydrogen phosphate

Dihydrogen phosphate

Name

Hydrogen sulfate (Bisulfate)

Chromate

Ion

Forming Chemical Bonds

• According to the Lewis model– an atom may lose or gain enough electrons to

acquire a filled valence shell and become an ion. An ionic bondionic bond is the result of the force of attraction between a cation and an anion.

– an atom may share electrons with one or more other atoms to acquire a filled valence shell. A covalentcovalent bondbond is the result of the force of attraction between two atoms that share one or more pairs of electrons.

Forming an Ionic Bond

• In forming sodium chloride, NaCl

– we use a single-headed curved arrow to show this transfer of one electron

Na + Cl Na+ Cl -

+Na+(1s22s22p6)

Cl(1s22s22p63s23p5)+Na(1s22s22p63s1)

Cl-(1s22s22p63s23p6)

Sodium atom Chlorine atom

Sodium ion Chloride ion

Formulas of Ionic Compounds

• The total number of positive charges must equal the total number of negative charges– lithium ion and bromide ion form LiBr

– barium ion and iodide ion form BaI2

– aluminum ion and sulfide ion form Al2S3

– sodium ion and bicarbonate ion form NaHCO3

– potassium ion and phosphate ion form K3PO4

Naming Ionic Compounds

• Binary ionic compounds– the name of metal from which the positive ion is

formed followed by the name of the negative ion; subscripts are ignored

– AlCl3 is aluminum chloride

– LiBr is lithium bromide

– Ag2S is silver sulfide

– MgO is magnesium oxide– KCl is potassium chloride

Naming Ionic Compounds

• Binary ionic compounds of metals that form two different cations– for systematic names, use Roman numerals to

show charge on the metal ion; for common names (not used in this class), use the -ous, -ic suffixes

– CuO is copper(II) oxide; cupric oxide– Cu2O is copper(I) oxide; cuprous oxide– FeO is iron(II) oxide; ferrous oxide– Fe2O3 is iron(III) oxide; ferric oxide

Naming Ionic Compounds

• Ionic compounds that contain polyatomic ions– name the positive ion first followed by the name of

the negative ion– NaNO3 is sodium nitrate– CaCO3 is calcium carbonate– NaH2PO4 is sodium dihydrogen phosphate– NH4OH is ammonium hydroxide– FeCO3 is iron(II) carbonate; ferrous carbonate– Fe2(CO3)3 is iron(III) carbonate; ferric carbonate– CuSO4 is copper(II) sulfate; cupric sulfate

FUNDAMENTALS OF COVALENT BONDING

Forming a Covalent Bond• A covalent bond is formed by sharing

one or more pairs of electrons– the pair of electrons is shared by both

atoms and, at the same time, fills the valence shell of each atom

– example:example: in forming H2, each hydrogen contributes one electron to the single bond

+H H

the single line represents a shared pair of electrons

.. H H

COVALENT BONDING

Figure 4.9. Energy Relationships in Covalent Bonds, H-H

COVALENT BONDS IN COMPOUNDSCovalent bonding of H Atoms to C and N Atoms

Lewis Structures

Covalent Bonds in H2O and HF

Compounds of Si, P, S, and Cl with H

Compounds of air pollution

CO, NO2, O3, SO2

Compounds that do not Conform to the Octet Rule

SOME OTHER ASPECTS OF COVALENT BONDINGSingle covalent bonds consist of 2 shared electrons

Double covalent bonds consist of 4 shared electrons

Triple covalent bonds consist of 6 shared electrons

Lengths and Strengths of Covalent BondsBond type: Single Double Triple

in C2H6 in C2H4 in C2H2

Bond length: 154 pm 134 pm 120 pm(pm stands for picometers)

Bond strength: 348 kJ/mol 614 kJ/mol 839 kJ/mol

Stronger, shorter bonds

Chemical bonds may absorb infrared radiation

• Higher frequencies for shorter, stronger bonds

Representation of a bond as a spring, Figure 4.14.

Electronegativity and Covalent BondingElectronegativity refers to the ability of a bonded atom to attract electrons to itself

Sharing Electrons — UnequallyFor the HCl molecule, the large Cl nucleus has a relatively much stronger attraction for the electrons in the bond

• Cl end of the molecule has more of a negative charge

• Polar covalent bond

Nonpolar covalent bonds are formed between atoms of the same element or atoms with similar electronegativies

H:H

Nonpolar bond

Molecular Compounds

• Molecular compound:Molecular compound: a compound in which all bonds are covalent

• Naming binary molecular compounds– the less electronegative element is named first – prefixes “di-”, tri-”, etc. are used to show the number of

atoms of each element; the prefix “mono-” is omitted when it refers to the first atom, and is rarely used with the second atom. Exception: carbon monoxide

– NO is nitrogen oxide (nitric oxide)– SF2 is sulfur difluoride– N2O is dinitrogen oxide (laughing gas)

Naming Cations

Fe3+

Fe2+

Hg+

Hg2+

Cu2+

Cu+ Copper(I) ionCopper(II) ion

Iron(II) ionIron(III) ion

Mercury(I) ionMercury(II) ion

Cuprous ionCupric ion

Ferrous ionFerric ion

Mercurous ionMercuric ion

Cupr- from cuprum, the Latinname for copper

Hg from hydrargyrum, theLatin name for mercury

IonSystematic name

Common name

Origin of the symbol of theelement or the common name of the ion

Ferr- from ferrum, the Latinname for iron

Sn2+

Sn4+

Tin(II) ionTin(IV) ion

Stannous ionStannic ion

Sn from stannum, theLatin name for tin

Do

No

t Use

Naming Anions

• For monatomic (containing only one atom) anions, add “ide” to the end– here are the monatomic anions we deal with most

often

Anion

F-

Cl-

Br-

I-

O2-

S2-

Stemname

fluorchlorbromiodoxsulf

Anionname

fluoridechloridebromideiodideoxidesulfide

Polyatomic Ions

– common names, where still widely used, are given in parentheses

NH4+

OH-

NO2-

NO3-

CH3COO-

CN-

MnO4-

CO32-

HCO3-

SO32-

HSO3-

SO42-

PO43-

HPO32-

H2PO4-

HSO4-

CrO42-

Ammonium

HydroxideNitrite

NitrateAcetate

Cyanide

Permanganate

Carbonate

Hydrogen carbonate (Bicarbonate)

IonName

SulfiteHydrogen sulfite (Bisulfite)

Sulfate

Phosphate

Hydrogen phosphate

Dihydrogen phosphate

Name

Hydrogen sulfate (Bisulfate)

Chromate

Ion

Forming Chemical Bonds

• According to the Lewis model– an atom may lose or gain enough electrons to

acquire a filled valence shell and become an ion. An ionic bondionic bond is the result of the force of attraction between a cation and an anion.

– an atom may share electrons with one or more other atoms to acquire a filled valence shell. A covalentcovalent bondbond is the result of the force of attraction between two atoms that share one or more pairs of electrons.

Forming an Ionic Bond

• In forming sodium chloride, NaCl

– we use a single-headed curved arrow to show this transfer of one electron

Na + Cl Na+ Cl -

+Na+(1s22s22p6)

Cl(1s22s22p63s23p5)+Na(1s22s22p63s1)

Cl-(1s22s22p63s23p6)

Sodium atom Chlorine atom

Sodium ion Chloride ion

Formulas of Ionic Compounds

• The total number of positive charges must equal the total number of negative charges– lithium ion and bromide ion form LiBr

– barium ion and iodide ion form BaI2

– aluminum ion and sulfide ion form Al2S3

– sodium ion and bicarbonate ion form NaHCO3

– potassium ion and phosphate ion form K3PO4

Naming Ionic Compounds

• Binary ionic compounds– the name of metal from which the positive ion is

formed followed by the name of the negative ion; subscripts are ignored

– AlCl3 is aluminum chloride

– LiBr is lithium bromide

– Ag2S is silver sulfide

– MgO is magnesium oxide– KCl is potassium chloride

Naming Ionic Compounds

• Binary ionic compounds of metals that form two different cations– for systematic names, use Roman numerals to

show charge on the metal ion; for common names (not used in this class), use the -ous, -ic suffixes

– CuO is copper(II) oxide; cupric oxide– Cu2O is copper(I) oxide; cuprous oxide– FeO is iron(II) oxide; ferrous oxide– Fe2O3 is iron(III) oxide; ferric oxide

Naming Ionic Compounds

• Ionic compounds that contain polyatomic ions– name the positive ion first followed by the name of

the negative ion– NaNO3 is sodium nitrate– CaCO3 is calcium carbonate– NaH2PO4 is sodium dihydrogen phosphate– NH4OH is ammonium hydroxide– FeCO3 is iron(II) carbonate; ferrous carbonate– Fe2(CO3)3 is iron(III) carbonate; ferric carbonate– CuSO4 is copper(II) sulfate; cupric sulfate

THE NAMES OF CHEMICAL COMPOUNDSBinary Molecular Compounds

Prefixes for relative numbers of atoms, such as penta for 5

First part of name is that of the first element in the compound

Second part of name is that of second element with ide ending

Examples:

• SO2: sulfur dioxide • N2O5: dinitrogen pentoxide

Names of Ionic Compounds

• When only two ions are involved, prefixes are not necessary because the ion charges determine the formula

• Al2(SO4)3 is aluminum sulfate, not dialuminum trisulfate

Prefixes can be used to specify variable numbers of ions

• NaH2PO4: Sodium dihydrogen phosphate

ACIDS, BASES, AND SALTSAn acid is a substance that dissolves in water to produce H+

(aq)

Acids with H and another element are hydro-ic acids

Variable amounts of O are shown with prefixes and suffixes as shown by the Cl-containing acids below:

• HCl: Hydrochloric acid

• HClO: Hypochlorous acid

• HClO2: Chlorous acid

• HClO3: Chloric acid

• HClO4: Perchloric acid

Bases

A base is a substance that contains OH- ion or produces it in water

• NaOH and Ca(OH)2 contain OH- ion

• NH3 produces OH- ion when dissolved in water

NH3 + H2O NH4+ + OH-

Bases containing OH- are named for the cation plus “hydroxide”

• Ca(OH)2: Calcium hydroxide

Acids and Bases

When an acid dissolves in water, the H+ concentration _____________ and the OH- concentration _____________.

When an base dissolves in water, the H+ concentration _____________ and the OH- concentration _____________.