Chapter 14 - Part 1

3 types of bonding

1. Metal with metal → Electron pooling and metallic bonding

2. Nonmetal with nonmetal → Electron sharing and covalent bonding

3. Metal with nonmetal → Electron transfer and ionic bonding

What is electromagnetic energy composed of?

Two orthogonal vectors → an electric wave and a magnetic wave

Aufbau principle

Electrons are assigned to shells and subshells in increasingly higher energy

Hund’s rule of maximum multiplicity

Electrons occupy orbitals singly first, then pair up

Delocalized electron bonding theory/Molecular orbital theory

Wave functions (orbitals) mic to form bonding combinations (constructive interference) and anti-bonding combinations (destructive interference).

Two ways of combining atomic orbitals

1. Constructive interference → Promotes bonding

2. Destructive interference → Decreases bonding

Which molecular orbital has higher energy?

The antibonding orbital; most of the electron density is outside the internuclear region, so electrons don’t shield one nucleus from the other.

MO bond order

Why doesn’t He2 exist?

MO BO = 0

Homonuclear diatomic vs. heteronuclear diatomic

What kind of bonding is H2?

Covalent

What atom is the most abundant in the universe?

Hydrogen (~90% of all atoms in the universe)

Hydrogen is the only element whose isotopes are each given a different symbol and name:

1H = protium (one proton, one electron)

2H = deuterium (one proton, one neutron, one electron)

3H = tritium (one proton, two neutrons, one electron)

How was deuterium produced?

The big bang → too fragile to survive fusion conditions of stars

Hydrogen cannot be….

satisfactorily classified in any group.

→ It has similarities to group one metals (+1 oxidation state) and group 17 non-metals (diatomic in elemental form and forming H-).

Hydrogen is found in ___ formal oxidation states.

3 (0, +1, -1)

Why does hydrogen make a good fuel?

Flammable and lightweight

Describe hydrogen’s melting and boiling points

Very low! (>20K)

How does hydrogen form H2O?

Combustion (This direction is voltaic.)

Main reactions for hydrogen synthesis (write the reaction)

1. Electrolysis of water

2. Steam-methane reforming reaction

3. Water-gas shift reaction

Does “hydride” automatically mean -1 formal charge?

No! Nonmetal hydrides are covalent compounds.

Does “hydride” automatically mean -1 oxidation state?

No! The most electronegative atom is assigned the -1 oxidation state.

Predict the products of H2 and F2

HF (g)

Predict the products of H2 and Cl2

HCl (g)

Predict the products of H2 and O2

H2O (g)

Predict the products of H2 and S8.

H2S (g)

Predict the products of H2 and N2

NH3 (g)

Atoms that are ___ in size have more energetically favorable reactions.

similar (formation of HF vs. HCl)

Strength of N2 triple bond

1000 kJ/mol

Group 1 and 2 hydrides are…

• Ionic and form from the elements

• Basic

• H charge = -1

H2 is only reduced when in the presence of…

very strong reducing agents

What does the reaction between an ionic hydride and water look like?

H- from hydrides is a ___.

reducing agent

Metallic hydrides

• Also called interstitials

• Not ionic → H atom occupies spaces between metal atoms

• ex. PdHx (no formal charge!)

Which group of metals has the lowest melting point and boiling point?

Group 1A/Alkali metals

What do the Alkali metals look like?

Soft, silvery metallic solids

Alkali metals have ___ radii and ___ densities.

large; low

Alkali metals are ___ ___ agents.

strong reducing

How are Alkali metals found?

Salts (because they are so reactive)

How are Alkali metals isolated?

Electrolysis

G1 metals react with hydrogen (H2 gas) to form…

ionic hydrides

G1 metals react with halogens to form…

ionic halides.

Why is Li+ different?

High charge-to-size ratio causes significant covalent character (ex. LiCl)

Charge density

Charge-to-size ratio

All G1 metals react with ___, but…

O2 gas; form different products depending on the metal

Lithium reacts with oxygen to form…

lithium oxide (Li2O)

Sodium reacts with oxygen to form…

sodium peroxide (Na2O2)

K, Rb, and Cs react with oxygen to form…

metal superoxides (MO2) (ex. KO2)

What is a superoxide ion?

One oxygen has a -1 charge. The other is a radical.

What is a peroxide ion?

Describe Alkali metals reaction with water.

• Highly spontaneous

• Violently reacts to form hydroxide and H2 (g)

Which G1 metal reacts with N2?

Li; gives metal nitride (Li3N) → unique among all Alkali metals!

Why is Be different from other alkaline earth metals?

High charge-to-size ratio → Very hard metal, toxic, compounds mostly covalent

Beryllium is an incredible ____.

Lewis acid

Why aren’t G2 elements as strong reducing agents as G1?

They have to lose two moles of electrons to be oxidized.

BeO is ___.

amphoteric

What does BeCl2 (s) actually look like?

There are bridge bonds. (Cl bridges Be atoms)

Describe the difference in bonding between BeCl2 and MgO/MgCl2.

BeCl2 is a covalent network solid. MgO and MgCl2 are ionic compounds.

Group 2 elements make __ when they react with oxygen.

oxides

Ba will also make ___ when it reacts with oxygen.

peroxide

Larger group two elements + water?

Reduce H2O to displace H2 gas → Violent reaction (like G1)

Group 2 elements react with N2 to make __.

metal nitrides (Mg at all T, other metals at only high T)

Nitride ion charge

-3

Group 2 metals react with CO2 to make…

metal oxide

Group 2 oxides react with CO2 to form…

carbonates

All group 2 carbonates…

decompose with heat.

Limestone

CaCO3 (s)

Lime

CaO(s)

Slaked lime

Ca(OH)2 (aq)

How do we get slaked lime?

1. Heat limestone

2. Add water

Why do lithium and magnesium have a diagonal relationship?

Similar charge density

What trends are highest in the bottom left of the periodic table?

• Ionic radius

• Atomic radius

• Metallic character

• Basic oxides

• Reductants

What trends are highest in the top right of the periodic table?

• Electron affinity

• Electronegativity

• Acidic oxides

• Ionization energy

• Oxidants

• Nonmetallic