chemical bonds:

- compounds are a chemical combination of two or more elements in exact ratios (result of a chemical bond, which is a lasting attraction between atoms, formed from a chemical reaction)

- valence electrons are the outermost electrons of an atom

- atoms bond according to their electronegativities (achieving stability by having full sets of valence electrons)

octet rules: a rule of thumb for non-transition metals (end up with 8 valence electrons)

- main group elements (groups 1, 2, 13-18)

- DO NOT USE FOR TRANSITION METALS!

- max. electrons would be 2 per PEL

- atoms would lose, gain, or share electrons order to achieve an octet

- atoms with an octet are more stable and have less energy overall

BARF:

- breaking a bond requires absorption of energy

- release of energy forms a bond

types of bonds:

- ionic bonds occur as a result of losing and gaining electrons

- covalent bonds (or molecular bonds) form from the sharing of electrons

- metallic bonds occur uniquely between atoms of metals

forming an ionic bond:

when metals react they

- lose e-

- become positively charged

- have smaller radii

- acquire the e- configuration of a noble gas

when nonmetals react they

- gain e-

- become negatively charged

- have larger radii

- acquire the e- configuration of a noble gas

so, ionic bonds typically form from metal + nonmetal because the ions are of opposite charge and are attracted to each other.

ionic solids:

- we call solid compounds formed through ionic bonds ionic solids

properties:

- solid, crystalline structure—organized structure

- high melting points

- electrical conductors when melted or in solution

covalent bonds:

- 2 nonmetals or a metalloid & nonmetal

- sharing of e-

nonpolar

- equal sharing

polar

- unequal sharing

typically illustrated as a line drawn between atoms

multiple covalent bonds:

one pair - 2

two pairs - 4

three pairs - 6

covalent “solids”:

- self-explanatory: compounds formed with covalent bonds

properties:

- soft

- low melting point

- poor conductors of heat and electricity

special type: network solid

- continuous covalently bonded compound

- extremely hard

- very high melting point

- poor conductors

metallic bonds:

- formed by the attraction of a single metal’s electrons and positively charged nuclei

- one of the reasons why metals are conductive are that they easily lose their electrons

- in a pure metal, the valence electrons can move freely between atoms, creating a “sea of electrons”

- metallic solids = metals

nonpolar covalent: difference of 0.4 or less

polar covalent: difference between 0.4 and 1.8

ionic: difference greater than 1.8

SNAP:

symmetric = nonpolar, asymmetric = polar (rotational)

intermolecular forces: forces that act between molecules (van der waals forces)

intramolecular forces: forces that act within a single molecule (a.k.a. bonds)

dipole-dipole forces:

- dipole—polar molecules

- “di” = two, + poles

- oppositely charged poles of different atoms will attract

hydrogen bonding: special type of dipole-dipole interaction

- hydrogen is particularly attracted to nitrogen, oxygen, and fluorine (the most electronegative atoms)

- stronger than dipole-dipole interaction

london dispersion forces: (weakest type of intermolecular force)

- caused by random movement of electrons to create temporary dipoles in molecules

- same attraction between poles then repeats the process with the next atom/molecule

- typically occurs in nonpolar molecules and single atoms (noble gases)

- scales with number of electrons/size of molecules and atoms