Chapter 3A
chemical bonds- what holds compounds
together
-bonds can be ionic or molecular/covalent
chemical formula- shows the kinds and number
of each element in a compound
ex- H2O
CO2
H3PO4
structural formula- uses lines to show bonds
ex- O
O═C═O
H
H
empirical formula- gives the relative number of
atoms of each element in a compound
-lowest whole number ratio
molecular formula- gives the actual number of
atoms of each element in a compound
ex- hydrogen peroxide
H2O2
emp. = HO (H and O in a 1:1 ratio)
mol. = H2O2
page 87 Ex 3.1 and FP 3.1
atomic elements- exist in nature as single atoms
-almost all the elements can exist as atoms
-called monatomic
molecular elements- cannot exist in nature as
one atom, cannot exist alone
-exist as molecules
H O N Cℓ Br I F
-called diatomic
Ions- particles with a charge (+ or -), they have
either lost or gained electrons
-in ions # of p+ ≠ # of ecation
-ion with a positive charge
-loses electrons
-metallic elements lose electrons
-look at Group # to get the charge for Groups 1A
to 3A
ex- sodium
Na1+ or Na+1 or Na+
aluminum
Aℓ3+
-sodium lost 1e-, aluminum lost 3 e**Most cations of the transition metals have
more than one charge
-these will need to be given to you
ex- Pb4+ lost 4e-a few have only one charge
Ag1+
Zn2+
Cd2+
-silver lost 1e-, zinc and cadmium each lost 2e-
anions
-ion with a negative charge
-gains electrons
-non-metallic elements gain electrons
-look at Group # - 8 to get the charge
ex- chlorine
Cℓ1arsenic
As3-chlorine gained 1e-arsenic gained 3e*Group 4 elements do not generally form ions,
Group 8 do not b/c they are inert
Naming Ions
Cations
-name is the same as the element with the word
ion
-back to examples
sodium ion
aluminum ion lead (IV) ion
Anions
-drop ending and add –ide and the word ion
-back to examples
-chloride ion
-arsenide ion
Try these!!
-name the ion/tell if it is a cation or anion
-tell the charge on the ion
-tell how e- the ion has lost or gained
Sr
I
Ca
K
P
B
S
polyatomic ions- made up or two or more atoms
that carry a charge
*most names end in –ite or –ate
Ionic Compounds
-compounds composed of cations and anions
-made up of a metal (cation) and a non-metal
(anion)
-usually solid crystals at room temp
-have high melting points
-are electrically neutral because # of p+ = # of eex- NaCℓ
KI
Ca3N2
formula unit- chemical formula for an ionic
compound
Molecular Compounds
-made up of two or more non-metals
Binary Molecular Compounds
-made up of two non-metals
Ex- CO, CO2, CCℓ4
-to name molecular compounds you use prefixes
Prefix
monoditritetrapentahexaheptaoctanonadeca-
# (subscript)
1
2
3
4
5
6
7
8
9
10
Naming Molecular Compounds
-look at subscript of each element and give each
element a prefix
-if first element has a 1 as the subscript, then it
does not get a prefix (omit mono-)
-second element gets prefix and ends in –ide
-if element begins with a vowel, drop the vowel
at the end of a prefix
**when writing formulas for molecular
compounds you DO NOT reduce subscripts
Try these!!
carbon monoxide
carbon tetrachloride
sulfur trioxide
tetriodine nonoxide
phosphorus pentafluoride
N2O
CℓO8
PCℓ3
NF3
SF6
S2Cℓ2
OF2
N 2O 4
Acids
-acids are compounds dissolved in water
-will have (aq) after the formula which means
aqueous or dissolved in water
-always begin with hydrogen (H)
Ex- HCℓ
H2SO4
H3PO3
Naming Acids
-you must look at what follows the hydrogen
-if it is a single element (ends in –ide), then you
use prefix hydro-, root of the element, -ic
ending and the word acid
ex- HCℓ
hydrochloric acid
-if what follows hydrogen ends in –ite, you just
add –ous ending to root of the polyatomic ion
and add acid
ex- H3PO3
phosphorous acid
-if what follows hydrogen ends in –ate, you just
add –ic ending to root of the polyatomic ion
and add acid
ex- H2SO4
sulfuric acid
Try these!!
HI
H2S
H2CO3
H2SO3
HNO2
HCℓO3