LECTURE 2

outer shell electrons of an atom

"an atom other than hydrogen tends to form bonds until it is surrounded by 8 valence electrons"
-strict followers: C, N, O, F

consists of the symbol of an element and one dot for each valence electron in an atom of the element

formed between two non-metal ions

- formed between a metal and non-metal atoms
- the electrostatic force that holds oppositely charged ions together in an ionic compound

-a force of attraction between the positive ions and the delocalized electrons

-array of positive ions (cations immersed in a sea of delocalized valence electrons

rigid and very ordered structure of cations and anions

make up the covalent bonds

non-bonding elctron pairs

-optimum distance between to nucle that leads to maximum stability
-higher bond length,higher bond strength lower bond order

-measured in terms of the energy released when a new bond is formed
-same energy is needed to break the same bond

- describes the unequal sharing of the electrons in a covalent bond
-as change in EN increases, bond polarity increases

the ability of an atom to attract toward itself the electrons in a chemical bond

angle between any two bonds in a molecule

predict the geometry of the molecule from the electrostatic repulsions between the electron (bonding and nonbonding) pairs

overall arrangement of electron pairs around the central atom

the geometry brought about the arrangement of atoms in space around the central atom

describes the covalent bond formation in terms of atomic orbitals
- formed by overlap of atomic orbitals, each of which contains one electronof opposite spin

1. Sigma Overlap
2. Pi Overlap

head-on overlap of two atomic orbitals

sideways overlap of two parallel p-orbitals

-fusion of atomic orbitals
-expansion of valence bond theory
- mixing of two or more atomic orbitals to form a new set of hybrid orbital

-4 groups attached from 2nd row elements
- tetrahedral geometry
- 109.5

-atoms of 2nd row elements with 3 attached groups
-trigonal planar
-120

-atoms of 2nd row elements with 2 attached groups
-linear
-180

- a molecule with unpaired electron spins
- strongly attracted by a magnetic field

- a molecule with only paired electron spins
- weakly repelled by a magnetic field