bonding & lewis structures

octet rule

atoms will lose or gain electrons in order to have 8 surrounding them

• 1-5 are exceptions — duet rule

isoelectronic series

ions & atoms with sample electron config. clustering around each other

Species	Number of Electrons	Electron Configuration
Ne	10	1s² 2s² 2p⁶
Na⁺	10	1s² 2s² 2p⁶
F⁻	10	1s² 2s² 2p⁶
Mg²⁺	10	1s² 2s² 2p⁶
Al³⁺	10	1s² 2s² 2p⁶

covalent bonding

atoms share electrons in overlapping regional of space

representations of molecules

• structural

• ball & stick

• condensed structural (tells how to do structural)

electron affinity

ability of an atom to attract electrons

electronegativity

ability of an atom to attract electrons in a bond — doesn’t have units

non-polar covalent bond

distribution of electrical charge is balanced between the two atoms

polar covalent bond

atoms have unequal attraction for electrons

polar moclecule

one end is slightly positive & other is slightly negative — dipole: two poles

• is oriented in presence of electric field

endothermic bonds

require more energy than given off

• ex. H₂O(s) - H₂O(l), decomp. of nature, photosynthesis & baking bread

exothermic bonds

releases more energy than required

• ex. Fe rusting, combustion reaction, respiration

EN range for polar bond

0.5 - 1.7

EN range for non-polar bond

< 0.4

EN range for ionic bond

> 1.7

types of covalent bonds

• single - H-H

• double - O-O

• triple - N-N

types of covalent bonds in terms of bond length & strength

• single: longest & weakest

• double: medium length & strength

• triple: shortest & strongest

reversible reaction

2H(g) + O₂ - H₂O(l) - freezer - H₂O(s)

catalyst

used to drive a reaction forward

resonance

use of two or more lewis structures represent the covalent bonding in a molecule

exceptions to octet rule

1. incomplete octet: less than 8

2. odd-e molecules: #ve is odd, impossible to reach octet

3. expanded octet: atoms in d block block, more ve than 8 — more than 8 be around central atom

van der waals forces

weakest intermolecular forces, consist of dipole-dipole & dispersion forces

dipole-dipole forces

attractive forces that occur between polar molecules

london dispersion forces

forces that occur between atoms and no polar molecules as result of electron motion

examples of molecules that demonstrate resonance

1. NO₃ - nitrate (ion)

2. NO₂ - (ion)

3. O₃ - ozone

   • include negative charges for ions