Organic Chemistry Chapter 1

Atoms

All matter is composed of

1. Nucleus (protons & neutrons; most of mass of atom)

2. Electron Cloud (electrons, volume of atom)

Two main components of atoms

number of protons = number of electrons

In a neutral atom…

Positively (fewer electrons than protons)

Cation is a ___ charged atom

Negatively (more electrons than protons)

Anion is a ____ charged atom

Isotopes (Isotopes also have different mass numbers)…..Mass number = number of protons + number of neutrons

Two atoms of the same element with a different number of neutrons are called ___

Similar in size and have same number of shells

Elements in the same row are ___

Similar electronic/chemical properties and same number of valence electrons

Elements in the same column have ___

Common Elements seen in O-Chem

shells closest to the nucleus

Electrons are first added to ___

S: Sphere of electron density; lower in energy (because closer to positively charged nucleus); only one S orbital per shell

P: dumbell shape (contains node of e density “no e density”); higher in energy than S orbital in same shell; 3 P orbitals per shell

S orbital has ___

P orbital has ___

Two electrons

Each orbital can have max of ___

8 electrons

Second shell or “second row” has capacity for ___

Valence electrons: only electrons that participate in chemical reactions

Outermost electrons are called ___ and what is special about them?

Atoms gain, lose, or share electrons to attain electronic configuration of the noble gas closest to them

One general Bonding rule:

Transfer of electrons (metal with nonmetal), typically known as salts

Usually occurs when elements on the far left combine with elements on the far right

Ionic bonding is ___

Sharing of electrons ( each atom contributes 1 e to the bond)

Occurs with elements in the middle like C, when they would have to gain or lose several e to form complete valence shell

Covalent bonding is ___

Atoms with one, two, three, or four valence e form 1,2,3, or 4 bonds respectively

Atoms with 5 or more valence e form enough for octet ( # bonds = 8 - valence e)

Rules for Number of Bonds

Unshared e = lone pair

Non-bonded pair of electrons =

RELEASES ENERGY, forming bonds ReLeAsEs energy!

REMEMBER!! Formation of bonds does what??

Step 1. Have a piece of paper ;D

THENNN, Step 1 arrange atoms next to each other in a logical manner

Step 2. count # of valence e

Step 3. Arrange e around the atoms

Step 4. assign formal charges (# of valence e - # of e an atom owns)

How to Draw Lewis Structures (e representation of molecules)

Isomers

Different molecules that have the same molecular formula

Constitutional Isomers

Same chemical formula; different connectivity

Resonance Structures (THEY ARE NOT ISOMERS)

Molecules that share the same molecule connectivity but have electrons that have moved

Resonance Hybrid

The actual structure of a molecule is the combination of resonance structures. This is called ___

Delocalize the electrons over two or more atoms, stabilizing the molecule

Importance of resonance structures?

1. differ in position of multiple bonds and non-bonded e

2. must have the same number of e

3. must be a valid Lewis structure (Octet Rule!)

Resonance Structure Rules

shows the movement of an e pair (SUPER IMPORTANT!)

Curved Arrow Notation

Decreases across a row (as size of atom decreases)

Increases down a column (as size of atom increases)

The shorter the bond, the stronger the bond

Bond Length

Determines the shape of the molecule

Takes into account atoms & lone pairs of e

VSPER Theory- e repel each other

Bond Angle

1. Two groups-linear

2. Three groups- trigonal planar (1 lone pair = bent)

3. Four groups- tetrahedral (1 lone pair = trigonal pyrimidal, 2 lone pair = bent)

Molecular Geometry for Second Row Elements

1. All atoms are drawn, no bond lines

2. Atoms drawn next to atom in which they are bonded

3. () used around similar groups bonded to same atom

Condensed Structures

1. Assume a carbon atom is at any “point” or end of the line

2. Assume enough H atoms to make each carbon atom tetravalent

3. Draw in all heteroatoms and the H atoms bonded to them

4. Draw double and triple bonds

Skeletal Structures