_____________________ that hold atoms together in compounds. The electrons involved in bonding are usually those in the _____________________ (valence) shell.

Most elements in compounds want to gain _____________________ configuration. They will do so by either _________________or _________________ electrons (_____________________ compounds) or by __________________electrons (_____________________ compounds)

Chemical bonds are classified into two types:

_____________________results from electrostatic attractions among ions; which are formed by the transfer of one or more electrons from one atom to another. (metals low χ with nonmetals high χ)

(χ = electronegativity)

_____________________ results from sharing one or more electron pairs between two atoms.

(nonmetals only similar χ )

Ionic Covalent

Melting Pt

Solubility◦ (polar solvents)

Solubility◦ (nonpolar solvents)

Conductivity◦ (molten & aqueous

solutions)

High Low

Soluble Insoluble

Insoluble Soluble

High Low

2 extremes in bonding

_________________ covalent bonds◦ electrons equally shared by the atoms

_________________ ionic bonds ◦ electrons are completely lost or gained by one of

the atoms

most compounds fall somewhere _________________ these two extremes

# of atoms in the molecule◦ _____________________ = 1 atom Ex. He

◦ _____________________ = 2 atoms Ex. O2

◦ _____________________ = 3 atoms Ex. O3

◦ _____________________ = many Ex. H2SO4 or S8

_____________________ : the mlcl is composed of only 1 kind of atom: O2, H2, P4

_____________________ : the mlcl is made up of more than 1 kind of atom: H2O

or Lewis dot formulas, a convenient bookkeeping method for ____________________ (electrons that are transferred or involved in chemical bonding) Only the electrons in the outermost s and p orbitals are shown as dots.

elements in the same group have same Lewis dot structures

For groups _____________________, the group number equals the # of _____________________electrons

Valence electrons determine the chemical and physical properties of the elements as well as the kinds of __________________ they form.

metals react with nonmetals to form ioniccompounds

_____________________ or positive (+) ions (metals)

◦ atoms have lost 1 or more electrons

_____________________ or negative (-) ions (nonmetals)

◦ atoms have gained 1 or more electrons

We can use Lewis formulas to represent the neutral atoms and the ions they form.

underlying reasons for LiF formation

1s 2s 2p

Li

F

becomes

Li+ [He]

F- [Ne]

Li+ ions contain two electrons◦ same number as helium

F- ions contain ten electrons ◦ same number as neon

Li+ ions are isoelectronic with _____________________ F- ions are isoelectronic with _____________________

*Isoelectronic species contain the _____________________number of electrons.

cations become isoelectronic with _____________________ noble gas

anions become isoelectronic with _____________________ noble gas

IIA metals with VIIA nonmetals, mostly ioniccompounds ~ exceptions - BeCl

2, BeBr

2, BeI

2 these

are covalent compounds

Be(s) + F2(g) BeF

2(s) electronically this is

happening

similarly for all of the IIA & VIIAM(s) + X

2 M2+ X

2-

IA + VIIA MX

IIA + VIIA MX2

IIIA + VIIA MX3

IA + VIA M2X

IIA + VIA MX

IIIA + VIA M2X

3

NaF

BaCl2

AlF3

Na2O

BaO

Al2S

3

IA + VA M3X

IIA + VA M3X

2

IIIA + VA MX

Na3N

Mg3P

2

AlN

H forms ionic compounds with IA and IIA metals (metal hydrides)LiH, KH, CaH

2, BaH

2,, etc.

other H compounds are covalent

_____________________ - the energy needed to separate oppositely charged ions. It is the energy that converts an ionic solid into widely separated gas ions

The _____________________ the lattice energy, the _____________________ the ionic bond.

The stronger the ionic bond the _____________________ in water at a given temperature, since the ions must _____________________ _____________________from one another and attach to water in order to dissolve.

_____________________ Law: for electrostatic attraction and/or repulsion. Applies to charged particles, magnets, gravitation, ionization energy, lattice energy

ions ofcenter between distance r

ionson charge of magnitude q

ionsbetween attraction of force F

wherer

qqF

2

~ ions with high (big)charges = F is large~ ions with small (little) charges = F is small

if opposite charges - The greater (bigger) the charges the greater the _____________________

if like charges - The _____________________ (bigger) the charges the greater the repulsion.

Also the closer the particles are the ________________the attraction or repulsion will be.

E = k

Energy = lattice energy,

Q1 = charge of positive ion

Q2 = charge of negative ion

r = bond length, the distance between the nuclei of the 2 ions – can also be _____________________ by the Period.

For r (Use the Period of the element that is _____________________ with the ion!

Na is in Period 3 and has 3 occupied energy levels. Na+ has lost an electron. It has 10 electrons and is isoelectronic with Ne in Period 2. Na+ has only 2 occupied energy levels.)

arrange these compounds in order of increasing attractions among ions

KCl, Al2O

3, CaO

1. Which has a stronger ionic bond, NaCl or KCl? Explain why.

The lattice energy of ________ is stronger, so this is the stronger ionic bond. Both have an electron charge of -1 and an effective nuclear charge of 1. But the valence electrons of _____are in the 3rd energy level, leading to a shorter bond length (measured as distance between ionic nuclei) and a stronger ionic bond than ________.

2. Which has a stronger ionic bond, NaCl or AlCl3? Explain why.

The ________ has a stronger ionic bond. Both have the same -1 charge for the chloride ion, and both Na+ and Al+3 are isoelectronic with Ne and therefore have 2 occupied energy levels. But the higher positive charge of the ________ ion leads to a stronger lattice energy and a stronger ionic bond.

3. Which is more soluble in 80° C water, NaCl or KCl? Explain why

You can dissolve more grams of ________ in 100 grams of 80° C water since it has a weaker ionic bond/lattice energy which requires less energy to separate/dissociate the ions from one another and allow them to attach to the polar water molecules.

4. Which is more soluble in 80° C water, NaCl or AlCl3? Explain why

________ is more soluble in 80° C water since it has a weaker ionic bond/lattice energy which requires less energy to separate/dissociate the ions from one another and allow them to attach to the polar water molecules.

5. Why is Na2O considered soluble in water while Al2O3 is not

Q2 for oxygen is the same for both compounds, a -2. Radius of oxygen is the same for both, and Na+ and Al+3 are isoelectronic. So the larger Q1

charge of Al+3 makes the lattice energy of the ________ greater, and since the ions stay bonded to one another it will not dissociate and dissolve.

extended three dimensional arrays of oppositely charged ions

_____________________ points because coulomb force is strong

covalent bonds formed when atoms share electrons

share 2 electrons - ___________________covalent bond

share 4 electrons - ___________________covalent bond

share 6 electrons - ___________________covalent bond

attraction is electrostatic in nature◦ lower potential energy when bonded

Covalent bonding may be explained by 2 different theories (more on this coming soon)

◦ ___________________ ___________________(VB) theory: each atom has electrons in atomic orbitals which overlap to form bonds

◦ ___________________ ___________________(MO) theory: the electrons belong to the molecule as a whole and are in molecular orbitals instead of belonging to each atom

The element needing the most electrons to fill its octet is usually the central atom

The most symmetrical skeleton is usually correct

Halogens and H always share one electron to complete outer shell

In ternary acids, H are bonded to O (ternary acids are oxy-acids: they contain H, O, and another nonmetal)

Carbon always obeys the octet rule

Carbon rarely has lone pairs of electrons. Exception: If it’s at the end of a molecule or ion. Ex. CN- , CO, CNO

When forming multiple bonds between atoms, both atoms donate the same number of electrons

Oxygen atoms normally bond to other nonmetals, not to each other

Oxygen can do several things depending on the mlcl.◦ Single bond by sharing an electron

◦ Single bond by accepting 2 electrons from another atom and not sharing at all

◦ Double bonds by sharing 2 of its electrons

___________________ : diatomic molecules◦ hydrogen, H2

◦ fluorine, F2

◦ nitrogen, N2

___________________ covalent bonds - electrons are shared equally

symmetrical charge distribution -must be the ___________________

______________to share exactly equally

Lewis dot representation H2 molecule formation

______________________________: diatomic molecules

hydrogen halides◦ hydrogen fluoride, HF

◦ hydrogen chloride, HCl

◦ hydrogen bromide, HBr

___________________ bonds - unequally shared electrons

•___________________ charge distribution

•different ___________________ ___________________

Some bonds are ___________________, Ex. HF

bondpolar very 1.9 Difference

4.0 2.1 ativitiesElectroneg

F H

1.9

Electron density map of HF

H-F◦ blue areas

low electron density

◦ red areas high electron density

polar molecules have separation of centers of negative and positive charge

Some bonds are only slightly polar, ex. HI

Electron density map of HI

H-I◦ blue areas

low electron density

◦ red areas

high electron density

notice that the charge separation is not as ______ as for HF◦ HI is only slightly polar

___________________ ___________________ elements achieve noble gas configurations in most of their compounds.

Lewis dot formulas are based on the ___________________.

H needs two electrons to have Helium's noble gas configuration, everything else wants 8

water, H2O

ammonia molecule , NH3

ammonium ion , NH4+

hydrogen cyanide, HCN

sulfite ion, SO32-

Two or more Lewis dot diagrams are needed to describe the bonding in a molecule or ion.

LDD for sulfur trioxide, SO3

three possible structures for SO3

invoke resonance◦ Double-headed arrows are used to indicate

resonance formulas.

flaw in our representations of molecules

no single or double bonds in SO3

all bonds are the same length

best picture

Carbonate, CO3-2

Nitrate, NO3-1

Nitrite, NO2-1

Sulfite ion, SO32-

Sulfur trioxide, SO3

Carbonate ion, CO32-

Nitrate ion, NO31-

Nitrite ion, NO21-

*Sulfate ion, SO42-

*Sulfur dioxide, SO2

*Ozone, O3

*Benzene, C6H6

The concept of formal charges helps us choose the correct Lewis structure for a molecule. If a ___________________ ___________________ has a high formal charge it’s not a very good one. A formal charge is assigned to each element in a compound

Formal charge = group # - (e- you can assign

to that atom)

Or F.C. = (valence e- ) – (# of bonds + # of

unshared e- )

Let’s assign formal charges for the elements in the L.D.D. from water, H2O to sulfite ion, SO3

2-

___________________ ___________________(σ) : result of head-on (end to end overlap, there is a free rotation around σ bonds.

___________________ ___________________(π) : result of side-on overlap of p orbitals. There is no free rotation around a π bond. The side –on overlap locks the molecule into place.

All ________________ bonds are sigma bonds: 1σ bond

All ________________ bonds: 1 σ bond, 1 π bond

All ________________ bonds: 1 σ bond, 2 π bonds

species in which the central element must have a share of more or less than 8 valence electrons to accommodate all substituents

compounds of the d- and f-transition metals

In cases where the octet rule does not apply, the elements attached to the central atom nearly always attain noble gas configurations. ◦ The central atom does not

Write LDD for BBr3

Write LDD for AsF5

Write LDD for XeF4