Ionic bonding and main group elements
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Ionic Bonding and Main-Group Elements. Chapter 6. ns 2 np 6. ns 1. ns 2 np 1. ns 2 np 2. ns 2 np 3. ns 2 np 4. ns 2 np 5. ns 2. d 10. d 1. d 5. 4f. 5f. Ground State Electron Configurations of the Elements. 8.2. Metals versus Nonmetals. Metals tend to form cations.

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Ionic Bonding and Main-Group Elements

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Ionic Bonding and Main-Group Elements

Chapter 6


ns2np6

ns1

ns2np1

ns2np2

ns2np3

ns2np4

ns2np5

ns2

d10

d1

d5

4f

5f

Ground State Electron Configurations of the Elements

8.2


Metals versus Nonmetals

  • Metals tend to form cations.

  • Nonmetals tend to form anions.


Ions and Ionic Radii01

  • Main-group metals donate electrons. from their valence shell.

    • Na: 1s2 2s2 2p6 3s1 = [Ne] 3s1

    • Na+: 1s2 2s2 2p6 =[Ne]

    • Mg: 1s2 2s2 2p6 3s2 = [Ne] 3s2

    • Mg2+: 1s2 2s2 2p6 =[Ne]

    • Al:1s2 2s2 2p6 3s2 3p1 = [Ne] 3s2 3p1

    • Al3+1s2 2s2 2p6 = [Ne]


-1

-2

-3

+1

+2

+3

Cations and Anions Of Representative Elements


Ions and Ionic Radii02

  • Main-group nonmetals accept electrons into their valence shell.

    • N: 1s2 2s2 2p3 = [He] 2s2 2p3

    • N3–: 1s2 2s2 2p6 = [He] 2s2 2p6

    • O: 1s2 2s2 2p4 = [He] 2s2 2p4

    • O2–: 1s2 2s2 2p6 = [He] 2s2 2p6

    • F:1s2 2s2 2p5 = [He] 2s2 2p5

    • F–:1s2 2s2 2p6 = [He] 2s2 2p6


Learning Check

Predict the charge of the following elements

Na [Ne]3s1

Na+ [Ne]

Atoms lose electrons so that cation has a noble-gas outer electron configuration.

Ca [Ar]4s2

Ca2+ [Ar]

Al [Ne]3s23p1

Al3+ [Ne]

H 1s1

H- 1s2 or [He]

Atoms gain electrons so that anion has a noble-gas outer electron configuration.

F 1s22s22p5

F- 1s22s22p6 or [Ne]

O 1s22s22p4

O2- 1s22s22p6 or [Ne]

N 1s22s22p3

N3- 1s22s22p6 or [Ne]


What neutral atom is isoelectronic with H- ?

Na+: [Ne]

Al3+: [Ne]

F-: 1s22s22p6 or [Ne]

O2-: 1s22s22p6 or [Ne]

N3-: 1s22s22p6 or [Ne]

Na+, Al3+, F-, O2-, and N3- are all isoelectronic with Ne

H-: 1s2

same electron configuration as He


Ions and Ionic Radii03

  • Transition metals lose their valence-shell s-electrons before losing their d-electrons. Electrons with the highest n-quantum number are lost first.

    • Fe:1s2 2s2 2p63s2 3p6 4s2 3d6= [Ar] 4s2 3d6

    • Fe2+:1s2 2s2 3s2 3p6 3d6 = [Ar] 3d6

    • Fe3+:1s2 2s2 3s2 3p6 3d5 = [Ar] 3d5


Learning Check

Predict the electronic structure of Mn2+ ?

When a cation is formed from an atom of a transition metal, electrons are always removed first from the ns orbital and then from the (n – 1)d orbitals.

Mn: [Ar]4s23d5

Mn2+: [Ar]4s03d5 or [Ar]3d5


Cation is always smaller than atom from which it is formed.

Anion is always larger than atom from which it is formed.

Size of Ions


Ionization energy is the minimum energy (kJ/mol) required to remove an electron from a gaseous atom in its ground state.

Ei1 + X(g) X+(g) + e-

Ei1 first ionization energy

Ei2 + X+(g) X2(g) + e-

Ei2 second ionization energy

Ei3 + X2+(g) X3+ +e-

Ei3 third ionization energy

Ei1 < Ei2 < Ei3


Ionization Energy

  • Abbreviation is Ei, it has units of kJ/mol.


Ionization Energy02

  • Ionization Energy Trend:

  • Ionization energies vary periodically; this is explained by the changes in Zeff.


Ionization Energy03


Electron Affinity

  • Energy change that occurs when an electron is added to an isolated atom in the gaseous state.

  • Abbreviation is Eea, it has units of kJ/mol.


X (g) + e- X-(g)

F (g) + e- X-(g)

O (g) + e- O-(g)

ΔH < 0

DH = -328 kJ/mol

DH = -141 kJ/mol


Electron Affinity02

  • Electron Affinity Trend:

  • Value of Eea results from interplay of nucleus-electron attraction, and electron–electron repulsion.


Electron Affinity03


Ionic Bonds and Ionic Solids01

  • Ionic bonds:

  • Form when an element with a small Eivalue comes in contact with an element with a negative Eeavalue.


Ionic Bonds and Ionic Solids

Sodium Chloride (NaCl):


Ionic Bonds and Ionic Solids04

Born–Haber Cycle for NaCl:


Ionic Bonds and Ionic Solids05

Born–Haber Cycle for MgCl2:


o

o

o

o

o

o

DHoverall = DH1 + DH2 + DH3 + DH4 + DH5

Born-Haber Cycle for Determining Lattice Energy


Calculate the net energy change that takes place on formation of KF(s) from the elements:K(s) + ½ F2(g)  KF(s) ΔH = ? kJ/mole


Calculate the net energy change that takes place on formation of KF(s) from the elements:K(s) + ½ F2(g)  KF(s) ΔH = ? kJ/mole

  • K(s)  K(g)Heat of sublimation+89.2 kJ/mol

  • K(g)  K+(g) + e­ First Ionization energy +418.8 kJ/mol

  • ½ [F2(g)  2 F(g)]Bond Dissociation Energy +79 kJ/mol

  • F(g) + e­ F­(g)First Electron affinity ­328 kJ/mol

  • K+(g) + F­(g)  KF(s)Lattice Energy in KF ­821 kJ/mol

    Sum = ­562 kJ/mol

    K(s) + ½ F2(g)  KF(s)ΔH = -562 kJ/mole


Alkali Metals

  • All have one s electron outside noble gas core.

  • All form M+ ions.


Electrolysis is the process in which electrical energy is used to cause a nonspontaneous chemical reaction to occur.


450°C in KCl

580°C in CaCl2

850°C

750°C

1A Preparation

  • Li & Na: Obtained by electrolysis.

    • 2 LiCl(l) 2 Li(l) + Cl2(g)

    • 2 NaCl(l)2 Na(l) + Cl2(g)

  • K, Rb, & Cs: Obtained by reductive distillation.

    • KCl(l) + Na(l) K(g) + NaCl(l)

    • 2 RbCl(l) + Ca(l)2 Rb(g) + CaCl2(l)

    • 2 CsCl(l) + Ca(l)2 Cs(g) + CaCl2(l)

  • 750°C


    1A Compounds01

    • Reaction with Halogens

      • 2 M(s) + X2 2 MX(s)

  • Reaction with Oxygen

    • Forms oxide (Li2O), peroxide (Na2O2), or superoxide (KO2)

  • Reaction with Hydrogen

    • 2 M(s) + H2 2 MH(s)

  • Reaction with Nitrogen

    • 6 Li(s) + N2 2 Li3N(s)


  • Alkaline Earth Metals

    • Smaller atomic radii than 1A.

    • Higher melting and boiling points than 1A.

    • Less reactive than 1A.

    • Exhibit covalent and ionic bonding character.

    • All are highly electropositive metals.

    • M2+ ions are small than M+.


    2A Compounds01

    • Reaction with Halogens

      • M(s) + X2 MX2(s)

  • Reaction with Oxygen

    • 2M(s) + O22 MO(s)

  • Reaction with Hydrogen

    • 2 Ca(s) + H2 2 CaH2(s)

  • Reaction with Water(only Ba and Radium are vigorous)

    • Ba(s) + H2O  Ba2+(aq) + 2 OH–(aq) + H2(g)


  • 3A Boron01

    • Elements in this group contain one semimetal, and four that are primarily metallic.

    • Boron is so different from the other elements in this group.

    • Boron is a semimetal, and forms covalent bonds.

    • It has many similarities to carbon and silicon.


    7A Halogens01

    • Halogens are reactive, & toxic nonmetals.

    • Properties decrease down the group.

    • HF is a weak acid, forms H–bonds.


    7A Halogens02

    • Fluorine and chlorine are strong oxidizing agents that are produced by electrolysis.

    • Fluorine is obtained from liquid HF.

    • Chlorine is obtained from molten NaCl or from the “chlor–alkali process.”


    Preparation of Chlorine

    • 6HCl + 2KMnO4 + 2H+ -->

      3Cl2 + 2MnO2 + 4H2O + 2K+


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