Chem Chapter 1

Front 1

Isomerism

Back 1

Different compounds that have the same molecular formula.

Front 2

Constitutional Isomers

Back 2

Are different compounds that have the same molecular formula but differ in their connectivity, that is, in the sequence in which their atoms are bonded together. (Have different properties: melting point, boiling point, and density)

Front 3

Ionic (or electrovalent) Bond

Back 3

Formed by the transfer of one or more electrons from one atom to another to create ions.

Front 4

Covalent Bond

Back 4

Bond that results when atoms share electrons.

Front 5

Octet Rule

Back 5

Tendency for an atom to achieve a configuration where its valence shell contains eight electrons.

Front 6

Electronegativity

Back 6

Is a measure of the ability of an atom to attract electrons. (Increasing electronegativity form right to left and bottom to top) FONCl

Front 7

Formal Charges

Back 7

The arithmetic sum of all of the formal charges equals the total charge on the molecule or ion. Calculating formal charges: subtract the number of valence electrons assigned to an atom in its bonded state from the number of valence electrons it has as a neutral free atom.

Front 8

Resonance Theory

Back 8

States that whenever a molecule or ion can be represented by two or more Lewis structures that differ only in the position of the electrons, two things will be true: 1. none of these structures, which we call resonance structures or resonance contributors, will be a correct representation for the molecule or ion. None will be in complete accord with the physical or chemical properties of the substance. 2. The Actual molecule or ion will be better represented by a hybrid (average) of these structures.

Front 9

Node

Back 9

Where a wave is exactly at the average level, the wave function will be zero.

Front 10

Reinforce

Back 10

Waves of the same phase sign meet each other, adding together and resulting in a larger wave.

Front 11

Interfere

Back 11

If waves of opposite sign meet they subtract from each other, and the resulting wave is smaller than either individual wave.

Front 12

Relationship of # of Nodes & Energy

Back 12

The greater the number of nodes, the greater the energy.

Front 13

Aufbau Principle

Back 13

Orbitals are filled so that those of lowest energy are filled first. (Aufbau is German for “building up”.)

Front 14

Pauli Exclusion Principle

Back 14

A maximum of two electrons may be placed in each orbital but only when the spins of the electrons are paired. An electron spins about its own axis.

Front 15

Hund’s Rule

Back 15

When we come to orbitals of equal energy (degenerate orbitals) such as the three p orbitals, we add one electron to each with their spins unpaired until each of the degenerate orbitals contains one electron. (This allows the electrons, which repel each other, to be farther apart.) Then, we begin adding a second electron to each degenerate orbital so that the spins are paired.

Front 16

Heisenberg Uncertainty Principal

Back 16

we cannot know simultaneously the position and momentum of an electron.

Front 17

Atomic and Molecular Obitals Combine

Back 17

the number of molecular orbitals that results always equals the number of atomic orbitals that combine.

Front 18

Bonding Molecular Orbital

Back 18

contains both electrons in the lowest energy state, or ground state, of a hydrogen molecule.

Front 19

Antibonding Molecular Orbital

Back 19

contains no electrons in the ground state of the molecule. It is formed by interaction of orbitals with opposite phase signs.

Front 20

LCAO

Back 20

(linear combination of atomic orbitals)

Front 21

Sigma (σ) Bond

Back 21

bond formed from the overlap of a sp3 orbital and a 1s orbital. Also is a general term in which orbital overlap gives a bond that is circularly symmetrical in cross section when viewed along the bond axis. All purely single bonds are sigma.

Front 22

Alkenes

Back 22

Hydrocarbons whose molecules contain a carbon-carbon double bond. Ex. Ethene also called Ethylene (C2H4) and Propene also called propylene (C3H6)

Front 23

Stereoisomers

Back 23

differ only in the arrangement of their atoms in space are often called cis-trans isomers.

Front 24

Alkynes

Back 24

Hydrocarbons in which two carbon atoms share three pairs of electrons between them. Ex. Ethyne (C2H2) and propyne (C3H4)

Front 25

Atomic Orbital (AO)

Back 25

corresponds to a region of space about the nucleus of a single atom where there is a high probability of finding an electron.

Front 26

Molecular Orbital (MO)

Back 26

overlapping atomic orbitals; correspond to regions of space encompassing two (or more) nuclei where electrons are to be found.

Front 27

Pi (π) Bond

Back 27

part of double and triple carbon-carbon bonds, is one in which the electron densities of two adjacent parallel p orbitals overlap sideways to form a bonding pi molecular orbital.

Front 28

VSEPR (valence shell electron pair repulsion theory)

Back 28

1. We consider molecules (or ions) in which the central atom is covalently bonded to two or more atoms or groups. 2. We consider all of the valence electron pairs of the central atom-both those that are shared in covalent bonds, called bonding pairs, and those that are unshared, called nonbonding pairs or unshared pairs. 3. Because electron pairs repel each other, the electron pairs of the valence shell tend to stay as far apart as possible. The repulsion between nonbonding pairs is generally greater than that between bonding pairs. 4.We arrive at the geometry of the molecule by considering all of the electron pairs, bonding and nonbonding, but we describe the shape of the molecule or ion by referring to the positions of the nuclei (or atoms) and not by the positions of the electron pairs.