Card Set Information
ch.5 Molecules & Compounds
What happens when
elements are combined?
*Compounds are composed of atoms in
Their properties completely change.
: Sodium: poisonous
= Sodium Chloride: table salt (safe)
and state his
Law of constant composition:
All samples of a given compund have the sam eproportions of their constituent elements.
(the composition of each compound is constant)
Diagram of the
for the decompositino of water.
18.0 g sample of water:
Mass ratio = 16.0 g O (oxygen) / 2.0 g H (hydrogen)
= 8.0, or 8.0:1.
Diagram of the water element.
H: symbol for hydrogen.
2: Subscript indicating 2 hydrogen atoms.
O: Symbol for oxygen.
*Implied subscript of 1 indicating 1 "oxygen" atom
Characteristic of subscripts.
The subscripts in a chemical formula represent the relative numbers of each type of atom in a chemical formula.
What is the general rule for the ordering of elements?
Ex: CO2? Not O2C
Elements on the left are generally listed before elements on the right.
The more metal-like element is listed first (elements to the left; Metals).
For columns, elements toward the
are more metal-like than elements toward the top.
Diagram for Mg(NO3)2.
Defining total # of subscripts.
Mg: symbol for magnesium
*Implied subscript indicating 1 Mg atom.
*(after N) Impled subscript indicating 1 nitrogen atom per NO3- group.
3: subscript indicating 3 oxygen atoms per NO3- group
2: subscript indicating 2, NO3-, groups.
Mg: 1 Mg
N: 1 x 2 = 2 N (implied 1 inside parentheses times 2 outside parentheses)
O: 3 x 2 = 6 O (3 insdide parantheses times 2 outside parentheses).
What are the 3 types of chemical formulas?
1) Empirical: gives the simplest whole-number ratio of atoms of each element in a compound
Hydrogen Peroxide: H2O2 (emp. is HO)
2) Molecular: gives the
number of atoms of each element in a molecule of the compound.
*3-d representation of models.
H2O2 (hydrogen peroxide)
3) Structural: uses lines to represent chemical bonds and shows how the atoms in a molecule are connected to each other.
Hydrogen Peroxide is H-O-O-H.
are either elements/compounds (ch.3),
be what two compositions?
be what to comositions?
Elements: atomic (Ne); Molecular (O2)
Compounds: Molecular (H2O); Ionic (NaCl)
Define (molecular element)
*Since molecular elements do not usually exist in nature w/ single atoms as their basic units, they must exist as diatomic molecules.
Two atoms of that element bonded together-as their basic units.
Hydrogen-H2 molecules; Oxygen-O2 molecules; chlorine-Cl2 molecules.
What are the elements that occur as
H2, N2, O2, F2, Cl2, Br2, I2
(hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine)
Contain one or more cations paired w/ one or more anions, the cations are metals and the anions are nonmetals.
KNO3 (metal + 2 nonmetals)
Compounds formed from two or more nonmetals (2+ nonmetals)
Ex: H2O (water); CO2 molecules (dry ice)
those that exist in nature w/ single atoms as their basic units.
do not normally exist in nature w/ single atoms as their basic units. They exist as
What is the difference between a
is a positively charged atom or group of atoms.
is a negatively charged atom or group of atoms.
Writing formulas for
1) Ionic compounds always contain positive & negative ions.
2) In the chemical formula, the sum of the charges of positive ions (cations) must always equal the sum of the charges of the negative ions (anions).
Naming Ionic Compounds (5.7)
are categorized into what two types?
1) Meta forms only one type of ion.
2) Metal forms more than one type of ion.
binary ionic compounds
containing a metal that forms only one type of cation.
Name of cation (metal); base name of anion (nonmetal) + -ide.
Consists of the cation, sodium, followed by the base name of the anion, chlor, with the ending, -ide. Full name: sodium chloride.
Naming binary ionc compounds containing a metal that forms more than one type of cation.
The full name for these types of compounds have the form:
(charge of cation (metal) in roman numerals in parentheses)) -->
base name of
(nonmetal) + -
FeCl3 = iron(III) chloride (iron is the cation followed by the charge of the cation in parentheses (III), followed by the
chlor, with the ending -
Full name: iron(III) oxide
*The charge of iron must be 3+ in order for the compound to be
(5.9, pg. 140) Naming ionic compounds containing a metal that forms more than one type of cation.
*Name the compound: PbCl4
Pb = cation
followed by the charge of the cation in parentheses (IV), followed by the
name of anion, chlor-, with the ending -
Full name: lead(IV) chloride.
The charge on Pb is 4+ because the charge on Cl is 1-. Since there are 4 Cl- anions, the Pb cation must be Pb4+.
Naming ionic compounds containing a polyatomic ion.
Ex: KNO3 = potassium nitrate
If there are more than 2 ions in the series, then the prefixes
, meaning "less than," and
-, meaning "more than," are used
ClO- is called
meaning "more oxygen than chlorate"
Naming Molecular Compounds
Ex: CO2 = carbon dioxide
[prefix][name of 1st element]
[prefix][name of 2nd element + -ide]
When writing the name of a molecular compound, as when writing the formula, the 1st is the more metal-like one.
The prefixes given to each element indicate the # of atoms present.
~CCl4 = carbon tetrachloride
~BCl3 = boron trichloride
Translate the following to the correct # of atoms in these prefixes.
1, 2, 3, 4, 5, 6, 7, 8, 9, 10
molecular compounds that produce H+ ions when dissolved in water.
*They're composed of H and one or more nonmetals in their formula.
Acids can be seperated into what two groups?
those containing only hydrogen and only a nonmetal.
those containing hydrogen, a nonmetal, and oxygen.
contains only 2 elements
***All depends on the # of elements in the acid.
hydro+base name of nonmetal + -ic + acid
Ex: define HCl(aq), HBr(aq)
hydrochlor -ic acid
hydrobrom -ic acid
-ite: name of oxyanion ends in -ite =ous
-ate: name of oxyanion ends in -ate =ic
The names of acids containing oxyanions ending with -ate takes this form:
[base name of oxyanion + -ic] + [acid]
Ex: H2SO3(aq) = sulfur
Ex(2): HNO3(aq) = nitr
Name the steps in order to identify and name the different categories of compounds in this chapter.
1) Decide whether the compound is
2) You can recognizer
compounds by the presence of a metal + a nonmetal.
compounds by two or more nonmetals only,
by the presence of hydrogen (written first) and one or more nonmetals.
Formula mass =
(# of atoms of 1st element in chemical formula x atomic mass of 1st element)
(# of atoms of 2nd element in chemical formula x atomic mass of 2nd element)
= 1 x (atomic mass C) + 4 x (atomic mass Cl)
=12.01 amu + 4(35.45 amu)
=12.01 amu + 141.80 amu
=153.8 amu (one decimal pt. addition rule of sfs)