atoms that lose or gain electrons become ions

cations have + charge

anions have – charge

cations and anions are attracted to each other by elecrostatic force.

bonds between ions form repeating patterns

can take the form of crystals when solid

usually a metal with a nonmetal formula units, NOT molecules

outer electrons (the highest energy level electrons) are called valence electrons.

the most stable valence electron configuration is that of noble gases

every atom will attempt to have its valence electrons conform to noble gas nearest it.

for most elements, this means the atom will have s2 and p6 filled when stable

Cl2Chlorine

formsa

covalentbondwithitself

ClClHowwilltwochlorineatomsreact?

ClClEach chlorine atom “wants” to

gain one electron to achieve an octet

ClClNeither atom will give up an electron,

chlorine is highly electronegative.

What’s the solution – what can theydo to achieve an octet?

ClCl

Cl Cl

Cl Cl

Cl Cl

Cl Cloctet

circle the electrons foreach atom that completestheir octets

Cl Cl

circle the electrons foreach atom that completestheir octets

octet

Cl ClThe octet is achieved byeach atom sharing theelectron pair in the middle

Cl ClThe octet is achieved byeach atom sharing theelectron pair in the middle

Cl ClThis is the bonding pair

Cl ClIt is a single bonding pair.The other electrons are

unshared pairs.

Cl ClIt is called a SINGLE BOND

Cl ClSingle bonds are abbreviated

with a dash

Cl ClThis is the chlorine molecule,

Cl2

O2

Oxygen is also one of the diatomic molecules

How will two oxygen atoms bond?

OO

OOEach atom has two unpaired electrons

OO

OO

OO

OO

OO

OO

Oxygen atoms are highly electronegative.

So both atoms want to gain two electrons.

OO

Oxygen atoms are highly electronegative.

So both atoms want to gain two electrons.

OO

OO

OO

OO

OO

OOBoth electron pairs are shared.

6 valence electronsplus 2 shared electrons

= full octet

OO

6 valence electronsplus 2 shared electrons

= full octet

OO

two bonding pairs,

OOmaking a double bond

OO=For convenience, the double bond

can be shown as two dashes.

OO

OO=This is the oxygen molecule,

O2

this is so

cool!!

formed by two or more nonmetals molecules are a neutral group of atoms

joined by covalent bonds in order to satisfy the octet rule (there are exceptions to this)› atoms are held together by sharing

valence electrons diatomic molecules are two of the

same atoms covalently bonded

atoms of different elements can covalently bond to form molecular compounds› tend to have lower melting and boiling

points than ionic compounds

single covalent bond- share a pair of electrons

often there is a pair of valence electrons that are not shared (unshared pair)

double or triple bonds share two or three pairs of electrons

shows how many atoms of each element› methane is

one carbon and four hydrogen

› CH4

does not tell you about the molecule’s structure (structuralformula)

refers to the idea that there are two or more valid electron dot formulas for a molecule

prefixes tell how many atoms of each element are present

still end with -ide vowel of the prefix is often dropped omit prefix mono- for the first

element carbon monoxide → CO nitrogen triiodide → NI3

CH4 methane

BCl3 boron trichloride

CO2 Carbon dioxide

Number Prefix1 mono2 di3 tri4 tetra5 penta6 hexa7 hepta8 octa9 nona

10 deca

First to name covalent compounds we need to know some Greek numerical prefixes.  It'd be a good idea to memorize these since they will be useful in many other classes.  

1. P2O5 a) phosphorus oxide

b) phosphorus pentoxide

c) diphosphorus pentoxide

2. Cl2O7 a) dichlorine heptoxide

b) dichlorine oxide

c) chlorine heptoxide

3. Cl2 a) chlorine

b) dichlorine

c) dichloride