Chem Chapter 6

chemical bond

mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atoms together

Nature aims to minimize potential energy

Atoms bond to achieve a more stable state by lowering their potential energy

Ionic Bonding occurs between what types of elements?

Metal and Nonmetal

In ionic bonding what happens to the electron?

It is transferred from the metal to the nonmetal

What happens to the charge of the metal in ionic bonding?

It loses an electron and becomes positively charged

What happens to the charge of the nonmetal in ionic bonding?

It gains an electron and becomes negatively charged

Covalent bonding

occurs between non-metals, sharing of electrons

Nonpolar Covalent definition

equal sharing of electrons

Polar covalent definition

unequal sharing of electrons

Nonpolar covalent E.N difference

0-0.3

Polar covalent E.N difference

0.3-1.7

Nonpolar covalent percentage ionic charecter

0%-5%

Polar covalent percentage ionic charecter

5%-50%

Polar

uneven distribution of charges

Octet rule

States that atoms lose, gain or share electrons in order to acquire a full set of eight valence electrons

Incomplete octet

stable with fewer than eight electrons

Expanded octet

when a molecule has more than 8 electrons around the central atom

Empirical formula

chemical formula that gives the simplest whole number ratio of atoms in a compound (lowest terms) Ex. C₆H₁₂O₆ → CH₂O

Hydrogen (H) octet exception

only needs 2 electrons to be full

Helium (He) octet exception

only needs 2 electrons to be full

Beryllium (Be) octet exception

only needs 4 electrons to be full

Boron (B) octet exception

Only needs 6 electrons to be full

Lithium (Li) octet exception

Forms Li⁺ ion with 2 electrons

Aluminimum (Al) octet exception

Sometimes stable with 6 electrons

Phosphorus (P) octet exception

Can have 10 electrons

Sulfur (S) octet exception

Can have 12 electrons

ionic compound properties

high MP (solid at room temp); poor conductors in solid state; good conductors when melted or dissolved; hard and brittle

Ionic compound

composed of positive and negative ions that are combined so that the numbers of positive and negative charges are equal

Formula unit

the simplest collection of atoms from which an ionic compound's formula can be established (Ex. NaCl)

Crystal lattice

A 3-dimensional geometric arrangement of the atoms or molecules or ions composing a crystal to minimize potential energy

Lattice energy

the energy released when one mole of an ionic crystalline compound is formed from gaseous ions (negative values indicate release)

polyatomic ion

A charged group of covalently bonded atoms

Why are ionic compounds hard but brittle?

The strong attraction between positive and negative ions holds them in a rigid, tightly packed arrangement. A large amount of energy is required to break these forces, making ionic compounds hard. If the layers move however, repulsion forces compete leading to a shattering of the layers

Delocalized electrons

electrons that are free to move through vacant orbitals

molecule

A group of atoms bonded together covalentently

molecular compound

a chemical compound whose simplest units are molecules

chemical formula

shows the elements in the compound and the ratio of atoms. Used for both ionic and molecular compounds.

molecular formula

a chemical formula of a molecular compound that shows the kinds and numbers of atoms present in a molecule of a compound

bond length

the average distance between the nuclei of two bonded atoms

bond energy

the energy required to break a chemical bond and form neutral isolated atoms

resonance

the bonding in molecules or ions that cannot be correctly represented by a single Lewis structure represneted with <--->

sea of electrons model

Simplified description of metallic bonding in which the valence electrons of metal atoms are delocalized and move freely throughout the solid rather than being tied to any specific atom.

enthlapy of vaporization

the amount of heat energy required to vaporize a metal

Why are metals good reflectors of light?

their mobile "sea of electrons", which can absorb and re-emit a wide range of light frequencies. When light strikes a metal surface, the free electrons oscillate and immediately release the absorbed energy as reflected light.

Why are metals good conductors of heat and electricity?

Metals conduct electricity because their free electrons move easily when a voltage is applied. They conduct heat as these electrons transfer energy quickly across the structure.

Strengh of metallic bonds depend on

number of valence electrons that can be delocalized, the charge of a metal ion(higher charge = higher strength), and the ionic radius of a metallic cation.

Why are metals malleable and ductile?

The layers of atoms in a metal can slide over each other

VSEPR theory

Valence-shell electron-pair repulsion theory; because electron pairs repel, molecules adjust their shapes so that valence electron pairs are as far apart as possible

Linear - Atoms bonded to central atom

2

Linear - Lone pairs of electrons

0

Linear - Type of molecule

AB₂

Trigonal-planar - Atoms bonded to central atom

3

Trigonal-planar - Lone pairs of electrons

0

Trigonal-planar - Type of molecule

AB₃

Bent or Angular (1 lone pair) - Atoms bonded to central atom

2

Bent or Angular (1 lone pair) - Lone pairs of electrons

1

Bent or Angular (1 lone pair) - Type of molecule

AB₂E

Tetrahedral - Atoms bonded to central atom

4

Tetrahedral - Lone pairs of electrons

0

Tetrahedral - Type of molecule

AB₄

Trigonal-pyramidal - Atoms bonded to central atom

3

Trigonal-pyramidal - Lone pairs of electrons

1

Trigonal-pyramidal - Type of molecule

AB₃E

Bent or Angular (2 lone pairs) - Atoms bonded to central atom

2

Bent or Angular (2 lone pairs) - Lone pairs of electrons

2

Bent or Angular (2 lone pairs) - Type of molecule

AB₂E₂

Trigonal-bipyramidal - Atoms bonded to central atom

5

Trigonal-bipyramidal - Lone pairs of electrons

0

Trigonal-bipyramidal - Type of molecule

AB₅

Octahedral - Atoms bonded to central atom

6

Octahedral - Lone pairs of electrons

0

Octahedral - Type of molecule

AB₆.

intermolecular forces

electrostatic interactions between molecules

dipole

a molecule that has two poles, or regions, with opposite charges

ion-ion

ionic molecule + ionic molecule, strongest intermolecular force

ion-dipole

the charge of an ion is attracted to the partial charge on a polar molecule (strongest dipole intermolecular force)

dipole-dipole

attractions between oppositely charged regions of polar molecules

hydrogen bonding

strongest type of intermolecular dipole-dipole attraction. Occurs between hydrogen and F, O or N

London dispersion forces

interaction between a momentary dipole and an induced dipole, caused by the random movement of electrons.

momentary dipole

a momentary lopsided electron cloud

induced dipole

caused when a momentary dipole comes near another electron cloud

nonpolar covalent intermolecular force

London Dispersion forces

ionic bond intermolecular force

ion-ion

Linear VSEPR Diagram

180 degrees

Trigonal-planar VSEPR Diagram

120 degrees

Bent or angular (1 lone pair) VSEPR Diagram

120 degrees

Tetrahedral VSEPR Diagram

109.5 degrees

trigonal-pyramidal VSEPR Diagram

107 degrees

Octahedral VSEPR Diagram

90 degrees

Bent or angular (2 lone paris) VSEPR Diagram

104.5 degrees

Triognal Bipyramidal VSEPR Diagram

90 and 120 degrees

hybridization

mixing of atomic orbitals of similar energies on the same atom to produce new hybrid atomic orbitals of equal eneriges.

How many hybrid orbitals are formed in sp hybridization?

2 hybrid orbitals.

What is the molecular geometry of sp hybridization?

Linear, with a bond angle of 180 degrees.

How many hybrid orbitals are formed in sp² hybridization?

3 hybrid orbitals.

What is the molecular geometry of sp² hybridization?

Trigonal planar with a bond angle of 120 degrees.

How many hybrid orbitals are formed in sp³ hybridization?

4 hybrid orbitals.

What is the molecular geometry of sp³ hybridization?

Tetrahedral with a bond angle of 109.5 degrees.

hybrid orbital

orbitals of equal energy produced by the combination of two or more orbitals on the same atom.

Ionic E.N Difference

1.7-3.3