Review ofChapter 6: Bonding

Bonds are forces of attraction between (-) electrons of one atom and the (+) nucleus of another atom, with 2 electrons in every bond

Forming bonds releases energy (exothermic)

Breaking bonds requires energy to be absorbed (endothermic)

Valence electrons are the outermost electrons, farthest from the nucleus, involved in bonding Elements in same column/group have same

valence # Right-most number listed in electron configuration

on periodic table tiles

Octet Rule: Most atoms want to have 8 valence electrons, and make bonds to gain a share of 8 H and He only want 2 total Noble gases already have 8, don’t react with others

Lewis Structures

Show # of valence electrons (1 to 8) around symbol for atom

Valence electrons drawn as dots

Electronegativity is how strongly an atom wants electrons and pulls on them in a bond

Listed on Table SNonpolar covalent bonds: difference between

EN values of two bonded atoms is 0Polar covalent bonds: difference between EN

values of two bonded atoms is between 0.1 and 1.7

Ionic bonds: difference between EN values of two bonded atoms is greater than 1.7

Covalent BondingNonmetals share electrons to form complete

octetsAny molecule with ONLY NONMETALS is

covalently bondedCan be single/double/triple bonds, with extra

electrons as lone pairs surrounding atoms

1. Count total # valence electrons in atoms of compound

2. Arrange atoms• Central usually has

lowest electronegativity, only once, isn’t H

3. Place single bonds

4. Add lone pairs to outsides, then center

5. Make more bonds if needed

1. Count total # valence electrons in atoms of compound

2. Arrange atoms• Central usually has

lowest electronegativity, only once, isn’t H

3. Place single bonds

4. Add lone pairs to outsides, then center

5. Make more bonds if needed

Ions form when atoms lose or gain electronsIons are just atoms with (+) or (-) charges

Metals lose e-, becoming (+) cations Ionization energy is energy needed to take an

electron away from an atom to make an ion Nonmetals gain e-, becoming (-) anions

In ionic bonding, metals give electrons away to nonmetals; charged ions then hang out near each other, attracted by different charges

Ionic Bonding

To draw Lewis structures for metal and nonmetal ions: When ions form, metal gets no e-, nonmetal gets a complete set of 8. Put each ion in brackets, and write the charge at top right (oxidation number from periodic table)

Metallic Bonding

Inside pieces of metal, (+) charged metal atoms are lined up neatly, with (-) electrons in constant motion, moving throughout the whole structure

This “sea of mobile electrons” holds the metal together, makes it a good electrical conductor, and makes it malleable (easily shaped)

Intermolecular Forces

Non-permanent, not “real bonds”Influence melting and boiling pointsElectrostatic attractions between different

chargesHydrogen bonding: temporary attraction

between an H atom and an atom of either F/N/O Responsible for many important properties of water