Dr. Lori Stepan Van Der Sluys 1 Chapter8 Part 2

Review Problem Below are successive Ionization Energies of an atom. Which atom is it?

I1 = 578 kJ I2 = 1820 kJ I3 = 2750 kJ

I4 = 11,600 kJ a) S b) Li c) Mg d) Ne e) Al

Dr. Lori Stepan Van Der Sluys 2 Chapter8 Part 2

Atomic Size

–How does size vary going down a group in the periodic table and why? (look at n and radius)

–How does size vary going across the periodic table and why? (look at Zeff and shielding)

–What is effective nuclear charge? What affects this? Which atoms/orbitals experience it more?

–Compare sizes of cations to parent ions.

–Compare sizes of anions to parent ions.

–Know how the size of isolectronic series are affected by shielding.

Ionization Energy

–What is the definition?

–What is the sign of ionization energy?

–Why?

–Know how IE varies going down a family and across the periodic table.

Dr. Lori Stepan Van Der Sluys 3 Chapter8 Part 2

Electron Affinity

–What is the definition?

–Which groups of elements have a negative EA and why?

–Which groups of elements have a positive EA and why?

Metal Reactivity

–How does metal reactivity vary going down a group in the periodic table?

–Why is metal reactivity related to IE?

–How is reactivity related to size?

–Which metal is most reactive? How did we demonstrate this in class?

Halogen Reactivity

–How does reactivity vary going down the group?

–Why is this order different than for metals?

–How is halogen reactivity related to electron affinity?

Dr. Lori Stepan Van Der Sluys 4 Chapter8 Part 2

Types of bonding; –What are the descriptions of the three types? –What are the differences?

Ionic Bonding –Know how to tell if a substance has ionic or covalent bonding –Know characteristics of ionic substances (conductivity, melting and boiling points, solubility, hardness) –Know how to illustrate valence electrons with a Lewis symbol –What is the octet rule? –Which two elements do not ever have an octet? –How many valence electrons do inert gases have?

Dr. Lori Stepan Van Der Sluys 5 Chapter8 Part 2

Cations and Anions –Know charges of common ions, how to use the periodic table to determine the preferred charge.

–Know the common cations in Table 2.4 (charge, formula, name)

–Know the common anions in Table 2.5 (charge, formula, name)

–Be able to name anions (Table 2.26)

–Be able to name acids from anions (Table 2.27)

–Be able to name compounds and ions formed from given elements (and write the molecular formula)

–Know which electrons are lost first when forming a transition metal ion.

Lattice Energy

–Why is formation of an ionic salt favorable?

–What is the definition of lattice energy?

–What is the sign of lattice energy, and why?

–Use Coulomb’s Law to explain why the lattice energy of two substances differs.

–Tell how ionic size is related to lattice energy.

–Tell how melting point is related to lattice energy.

Dr. Lori Stepan Van Der Sluys 6 Chapter8 Part 2

Chapter 8 Part 2: Covalent bonding

Read: BLB 2.6–2.8; 8.3-8.5

HW: BLB 8: 29, 37, 39

Packet 8:5, 6

Know:

Covalent Bonding

Electronegativity

Polarity

What Bonus Deadlines are Coming Up?? ______________________________________ ______________________________________

When is Exam 1?? ________________ Where is my section taking the Exam? _______________________________

o Data sheet in packet will be provided o Bring:

! pencils, ! student ID ! and a calculator—NO text-programmable

calculators or wireless devices

Dr. Lori Stepan Van Der Sluys 7 Chapter8 Part 2

Bonding in the H2 Molecule

Dr. Lori Stepan Van Der Sluys 8 Chapter8 Part 2

COVALENT BONDING When neither atom is "willing" to give up electrons (completely) atoms _____________ electrons: each atom has a _______________ configuration. Covalent Bond: • Bond strengths ~200-800 kJ/mole

Lewis Structures

" show how electrons are shared " shows atom ____________ " also display unshared electron pairs

lone pairs. •• ••

: Cl!Cl : •• ••

" tells where electrons are, like a census tells

where people are.

Dr. Lori Stepan Van Der Sluys 9 Chapter8 Part 2

Lewis Structures

For non-metals, the number of valence electrons in the neutral atom is the same as

the group number.

H2

HCl

NH3

NH4+

CH3CH2OH

Ne

CH4

Dr. Lori Stepan Van Der Sluys 10 Chapter8 Part 2

Multiple Bonds; Distinctive Properties Single Bond; Bond Order = ______ Double Bond; Bond Order = ______ Triple Bond; Bond Order = ______

CO2

N2

H2

N"N N=N N#N

l 1.47 1.24 1.10 Å

E 163 418 941 kJ/mole

bond length, l bond strength, E

Dr. Lori Stepan Van Der Sluys 11 Chapter8 Part 2

Bond Polarity Nonpolar covalent: electrons are shared equally (H2, Br2, Cl2) Polar covalent: unequal sharing of electrons (ICl) I$+

Cl$

-

Ionic: no sharing of electrons: (NaCl, KI) Na

+ Cl

-

Dr. Lori Stepan Van Der Sluys 12 Chapter8 Part 2

Electron sharing in covalent bonds depends on the electronegativity of atoms.

ELECTRONEGATIVITY:

NOT the same as electron affinity

• not directly measurable: use a relative scale.

Most electronegative: F (4.0)

Least electronegative: Cs (0.7)

Dr. Lori Stepan Van Der Sluys 13 Chapter8 Part 2

Electronegativity Periodic Trends: • ______________ going up group %

• ______________ from left to right &

• nonmetals are most electronegative

(F, O, N, Cl, Br, I)

• ______________ are least electronegative (especially active metals, Groups I and II)

Dr. Lori Stepan Van Der Sluys 14 Chapter8 Part 2

Remember the Order for

Electronegativity

For Our New Clambakes Bring Internationally-

Shipped Canned Hams, Please

Dr. Lori Stepan Van Der Sluys 15 Chapter8 Part 2

Electronegativity and Bonding

ionic: large difference in electronegativity NaCl KI

'EN ~ > ________

polar covalent: some difference in electronegativity ICl HCl

'EN between ________

Covalent: no difference in electronegativity. H2 Br2 I2 Cl2

'EN = ________

or very little difference: C!H, hydrocarbons

(assume covalent bonding) 'EN< ________

Dr. Lori Stepan Van Der Sluys 16 Chapter8 Part 2

Bond Polarity

Covalent Polar Covalent

Blue regions are low electron density, red is high electron density.

Dipole Moment Entire molecule can be polar, not just the bond.

µ = Qr

H F

H F

$+ $-

Dr. Lori Stepan Van Der Sluys 17 Chapter8 Part 2

Nomenclature and Electronegativity

• Name the less electronegative element first

• Name the more electronegative element

second, with -ide ending

Ionic compounds name the ions and charges

Molecular compounds use prefixes