Organic Chemistry chapter 1 terms

Schematic representations of molecules to show their molecular geometry.

Molecules with the same molecular formula but different molecular structures.

• Molecules with the same molecular formula but with different connectivity of atoms, e.g.
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The connections of atoms to other atoms in a molecular structure.

• A measure of the ability of an atom to attract electrons. Electronegativity increases going up and to the right on the periodic table.
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Bonds formed between atoms having a large difference in electronegativity, the more electronegative element "takes" the electron(s) from the less electronegative element. This typically occurs between a metal and a non-metal. The molecular orbitals are such that only one atom is contributing to the bonding orbital.

Covalent bonding occurs when two atoms have little difference in their electronegativities. This typically occurs between non-metallic atoms. Covalent bonds are formed by a sharing of electrons within molecular orbitals.

In organic chemistry single bonds refer to a covalent sigma bond.

In organic chemistry double bonds refer to a covalent sigma bond and a covalent pi bond between the same two atoms.

In organic chemistry triple bonds refer to a covalent sigma bond and two covalent pi bonds between the same two atoms.

• A representation of a molecule or ion showing the atomic symbol(s), bonding, and unshared electron pairs, e.g.
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The positive or negative charge on an atom within a molecule.

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• Ethanol

• CH₃CH₂OH
• Ethanol

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• Ethanol

• Molecules that have the same connectivity but differ in their arrangement of atoms in space, e.g.
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• 1) No single Lewis structure is the correct depiction of the molecule in question.
• 2) The actual molecule is shown by a hybrid of multiple structures.

Whenever a molecule, or ion, can be represented by two or more Lewis structures that differ only in the positions of the electrons then precepts of resonance theory must be applied.

The wave function is a calculation that determines the particular energy of an electron.

The square of the wave function yields a (x,y,z) probability of finding an electron in a particular region of space.

A region of space where the probability of finding an electron is large.

• A region of space about the nucleus of a single atom where the probability of finding an electron is large, e.g. the s orbital.
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• Combinations of atomic orbitals that result in a lower energy ground state for atoms in molecules, e.g. sp³ hybridization.
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Orbitals that exist due to the overlap of atomic orbitals (of the same phase) from two atoms. Molecular orbital formation causes bonding and antibonding orbitals to form, the bonding are always at a lower energy level.

• A graphic illustration of a molecule that shows where electron density is greatest and the furthest extent of overall electron density.
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• A graphic representation of charge distribution in a molecule or ion (red = negative / blue = positive).
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A model used for predicting molecular geometry based on estimations of bonding and non-bonding electron pairs.

Orbitals are filled with electrons so that those of the lowest energy are filled first.

A maximum of two spin-paired electrons may be placed in any one orbital.

When orbitals of the same energy are filled (e.g. the Px, Py, and Pz orbitals) one electron is added to each orbital before any are paired.