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Chapter 3 – Classification of Matter
 Elements – Distribution, Names, Symbols
 Elements - Metals, Nonmetals, Metalloids
 Diatomic Molecules
 Chemical Formulas
 Mixtures
Elements
 Element: A substance that cannot be
decomposed into simpler substances by
chemical means.
Make up our
chemical
alphabet.
Over 100
known
elements
Elements
 Element: Our building block of all substances.
 Numbered
in order of increasing complexity
•Elements through 92 are
known to occur in nature.
[with 4 exception
Technetium (43),
Promethium (61), Astatine
(85), Francium (87)]
•Above 92 only Plutonium
(94) occur in nature.
•Above 92 all elements
must be synthesized in the
laboratories in small
quantities
Elements
 Most substances can be
decomposed into two or more
simpler substance.
 Water = Hydrogen and Oxygen
 Sugar = Carbon, Hydrogen, and
Oxygen
 Salt = Sodium and Chloride
Elements
 The smallest particle of an element
that can exist is an atom,
 which
is also the smallest unit of an
element that can enter into a
chemical reaction.
 Atoms are made up of subatomic
particles that will be discussed later
in the semester.
Distribution of Elements
 Elements are distributed unequally in nature
 Ten
elements make up 99% of the mass of
the Earths Crust, seawater, and atmosphere

Oxygen is about 50% of this mass
 Two
elements are liquids at room
temperature

Bromine and Mercury
 Eleven

elements are gases
Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine,
Helium, Neon, Argon, Krypton, Xenon, and
Radon
 All
other elements are solids
Distribution of Elements
 Elements are
distributed
unequally in
nature



Figure a, shows
the distribution in
the glalaxies
Figure b, shows
the distribution in
Earths crust
Figure c, shows
the distribution in
Humans
Sources of Element Names
Greek- • Iodine: from the Greek iodes meaning
Color
violet.
Latin- • Fluorine: from the Latin fluere meaning
Property to flow. The fluorine containing ore
fluorospar is low melting.
German- • Bismuth: from the German
Color
weisse mass which means white mass.
Location • Germanium: discovered in 1866 by a
German chemist.
Famous- • Einsteinium: named for Albert Einstein.
Scientists
Symbols of the Elements
 Each element has an abbreviation.




Iodine is taken from Greek work iodes, meaning violet.
Bismuth is from German, weisse masse, white mass.
Germanium is due to it’s discovery by a German
Others are named in commemoration of famous
scientist
Symbols of the Elements
 Each element has an abbreviation –
Symbols
 Some
(14) have single letter
 The rest have 2 letters

The symbol stands for the element itself
 For one atom of the element
 For a particular quantity of the element
 Rules.
Symbols have either one or two letters
 If one letter – Capitalized
 If two letters – First letter capitalized – second
letter lower case

Rules governing symbols of the
elements are:
1.
Symbols have either one or two
letters.
2. If one letter is used it is
capitalized.
H carbon
C
hydrogen
3. If two letters are used, only Ba
Ne barium
neon
the first is capitalized.
Symbols of the Elements
Symbols and names are on the inside cover.
Possibly make flash cards to learn these symbols.
Metal, Nonmetals, and Metalloids
Metal, Nonmetals, and Metalloids
Metals
Most of the elements are metals
Solids at RT (except mercury)
Malleable – Can be hammered or rolled
into sheets.
Ductile – Can be Drawn into wires
High Melting point
High density
Combine with non-metals to form ionic
compounds
Often found as alloys – Homogenous
mixtures
Metal, Nonmetals, and Metalloids
A few of the less reactive metals such as
copper, silver and gold are found in the
free state.
 Metals can mix with each other to form
alloys.
 Brass is a mixture of copper and zinc.
 Bronze is a mixture of copper and tin.
 Steel is a mixture of carbon and iron.

Metal, Nonmetals, and Metalloids
Nonmetals
Low melting points and density
Generally poor conductors of heat and
conductivity
Combine with one another to form
molecular compounds
Metalloids
Properties are intermediate between
metals and nonmetals
Some are raw material for semiconductor
Metalloids







boron
silicon
germanium
arsenic
antimony
tellurium
polonium
Compounds
Compound: A substance with a
constant composition that can be
broken down into elements by
chemical processes.
 Atoms in a compound are always
whole number ratios
 Two types - molecular and ionic
Compounds
 Molecule – The smallest uncharged
individual unit of a compound formed
from 2 or more atoms
 Ion – Positively or negatively charged
atom or group of atoms.
 Held
together by attractive forces from
positively and negatively charged ions
Cation – Positively charged
 Anion – Negatively charged

Compounds can be classified as molecular or
ionic. Ionic compounds are held together by
attractive forces between their positive and
negative charges. Molecular compounds are
held together by covalent bonds.
Diatomic Molecules
 Special type of molecule
 Contain 2 atoms – alike or different
 Seven elements are diatomic molecules
 Hydrogen - H2
 Oxygen - O2
 Nitrogen - N2
 Fluorine - F2
 Chlorine - Cl2
 Bromine - Br2
 Iodine - I2
 Need to know these!!!!
Occurrence of Diatomic Molecules
Hydrogen
H
Not found in
nature.
Found in nature.
Hydrogen
Nitrogen
H2
N
Not found in
nature.
Found in nature.
Nitrogen
N2
Chemical Formulas
 Used as abbreviations for compounds
 Shows the symbols and the ratio of the elements
in a compound
H2O

Indicates 2 Hydrogens and one Oxygen
H2SO4

Indicates 2 Hydrogens, 1 Sulfur, and 4 Oxygen
 Water has the formula H2O.
• It does not contain free hydrogen, H2 or free
oxygen, O2.
• The H2 part of H2O means that 2 atoms of
hydrogen are combined with one atom of
oxygen in the water molecule.
H2
O2
H2O
chemical
formulas
Serve as abbreviations of the
names of compounds.
CaCl2
calcium
chloride
chemical
formulas
Tell which elements the
compound is composed of
and how many atoms of each
element are present in a
formula unit.
CaCl2
calcium
chlorine
chemical
formulas
Show the symbols of the atoms
of the elements present in a
compound.
CaCl2
Ca calcium
Cl chlorine
chemical
formulas
Show the ratio of the atoms of
the elements present in a
compound.
CaCl2
2 Cl
1 Ca
Chemical Formulas
 Formula of a compound contains the symbols of
all the elements
 Formula contains one atom of an element the
number 1 subscript is left out
 Formula contains more than one atom of the
same element – the number is indicated as a
subscript written to the right of the symbol of
that atom
 When a formula contains more than one group
of atoms occur as a unit – a parentheses is
place around the group with the number
subscripted
 Ca(NO3)2
Chemical Formulas
H3PO4
indicates
the element
oxygen (O)
indicates
indicates
the element indicates
4 O atoms
hydrogen (H) 3 H atoms
indicates
the element
phosphorous (P)
Chemical Formulas
indicates
the element
barium
indicates two
phosphate (PO 34 )
groups
Ba3(PO4)2
indicates three
Ba atoms
indicates the phosphate group
composed of one phosphorous
atom and four oxygen atoms
Chemical Formulas
Formulas written as H2O, H2SO4,
Ca(NO3)2 and C12H22O11 show only
the number and kind of each atom
contained in the compound; they do
not show the arrangements of the
atoms in the compound or how they
are chemically bonded to each other.
Concepts - Chapter 3
 Classify – elements, compounds, mixtures
 Write symbols or name for common elements
 Understand chemical formulas
 Differentiate between atoms, molecules, ions
 Know some characteristics of metals,
nonmetals and metalloids
 Recognize elements that occur as diatomic
molecules