CHAPTER 4 ELEMENTS AND ATOMS

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CHAPTER 4 ELEMENTS AND ATOMS
THE ELEMENTS
400 BC Greeks thought there were 4 elements
Earth, Wind, Fire, Water
2009 AD There are 117 known elements (94 that
occur naturally)
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Most Common Elements in Earths Crust Solid
Earth Atmosphere Universe
Oxygen Silicon Aluminum
Iron Nickel Magnesium
Nitrogen Oxygen Argon
Hydrogen Helium
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SYMBOLS FOR THE ELEMENTS Letters symbolize
elements 1st Letter always a capital 2nd
Letter always lower case
Co CO
Cobalt Carbon monoxide Sn
SN
Tin Sulfur a
little Nitrogen?
Some symbols come from Latin names
YOU MUST MEMORIZE THE 46 ELEMENTAL SYMBOLS ON
HANDOUT 1
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400 BC DEMOCRITUS
Proposed that all matter is composed of
indivisible particles ATOMS From the Greek
Atomos, meaning indivisible
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1803 JOHN DALTON
Proposed that matter is composed of atoms Atoms
could explain why compounds always have a
definite proportion by mass
Mass of Carbon Mass of Hydrogen
Ethyne
12 grams 1 gram
Ethene
12 grams 2 grams
Ethane
12 grams 3 grams
Suppose the elements carbon and hydrogen are
composed of atoms
Suppose carbon atoms weigh 12 times more than
hydrogen atoms
Ethyne is C1H1
Ethene is C1H2
Ethane is C1H3
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DALTONS ATOMIC THEORY
1 Elements are made of individual atoms
2 All atoms of a given element are the same
3 Compounds are formed when atoms of different
elements combine with each other
4 Atoms of one element cannot change into
atoms of another element
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• FORMULAS OF COMPOUNDS
• CHEMICAL FORMULA The representation of a
  compound or molecule using elemental symbols
• Writing formulas
• Each element present is represented by its
  elemental symbol
• A right subscript tells the number of atoms of
  each element
• Subscripts of 1 are not written

CS2 Na3AsO4 Zn(NO3)2 BaCl2.2H2O
1 barium atom 2 chlorine atoms 4 hydrogen
atoms 2 oxygen atoms
1 carbon atom 2 sulfur atoms
3 sodium atoms 1 arsenic atom 4 oxygen atoms
1 zinc atom 2 nitrogen atoms 6 oxygen atoms
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1897 J.J. THOMSON
Discovered that atoms consist of subatomic
particles
ELECTRONS Negatively charged subatomic particles
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Thomson Model of the Atom
PROTONS Positively charged subatomic particles
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1910 ERNEST RUTHERFORD Found that the atoms has
a small, positively charged core which contains
almost all of the atoms mass
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Rutherford Model of the Atom
NUCLEUS The dense, positive core of the atom
that contains protons
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1932 JAMES CHADWICK
Discovered a third subatomic particle
This subatomic particle was found the in nuclei
of atoms
NEUTRONS Neutral subatomic particles
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The Nuclear Model of the Atom
Location Charge Relative Masses
Around Nucleus - 1 Nucleus 1836 Nucleus 0 183
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Electron Proton Neutron
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1964 MURRAY GELL-MANN
Proposed that protons and neutrons are made of
smaller particles called
QUARKS
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ISOTOPES
All atoms of a given element contain the same
number of protons
ATOMIC NUMBER (Z) The number of protons in an
atom
? Atomic Number ? Atomic Symbol
Any atom with 1 proton is a hydrogen atom
Because atoms are electrically neutral, the
number of electrons must equal the number of
protons
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Hydrogen
Hydrogen
Hydrogen
All 3 are hydrogen atoms because they each have 1
proton
ISOTOPES Atoms of the same element (same number
of protons), but with different numbers of
neutrons
MASS NUMBER (A) The sum of the protons and
neutrons in an atom
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Protons Neutrons Electrons
1 1 1 0 1 2 1 1 1
1
2
3
Mass Number
Isotope Name
1H Hydrogen-1
2H Hydrogen-2
3H Hydrogen-3
Mass Numbers ARE NOT found on the Periodic Table
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Protons Neutrons Electrons
2 2 1 2 2 2
3
4
Mass Number
Isotope Name
3He Helium-3
4He Helium-4
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Find the number of protons, neutrons, and
electrons in each
Isotope Name
27Al
238U
Protons Neutrons Electrons
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THE PERIODIC TABLE
An arrangement of the chemical elements in order
of atomic number, with elements having similar
properties placed in columns
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1869 DMITRI MENDELEEV Developed the first
periodic table
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PERIOD or SERIES A row
GROUP or FAMILY A column
Elements in columns have similar properties
because they have the same number of valence
electrons
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METALS Physical Properties Metallic luster,
malleable, ductile, conductors of heat and
electricity Solids are brilliant white (or
silver) except copper (red) and gold (yellow),
mercury is a liquid
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NONMETALS Physical Properties Opposite of
metals Some are crystalline solids, bromine is a
liquid, and some are gases
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METALLOIDS Properties of metals and
nonmetals Border the diagonal line separating the
metals and nonmetals
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Hydrogen - A group of its own Group 1 - Alkali
Metals Group 2 - Alkaline Earth Metals Group 7
- Halogens Group 8 - Noble Gases Middle
Block - Transition Metals Extra Block - Inner
Transition Metals (Lanthanides and Actinides) Cu,
Ag, Au, Pt - Noble Metals
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• NATURAL STATE OF MATTER
• Most elements are ACTIVE, so they easily form
  compounds
• Matter is mostly a mixture of compounds, not
  elements
• INERT elements can be found in their elemental
  form
• Noble Metals Cu, Ag, Au, Pt
• Noble Gases He, Ne, Ar, Kr, Xe, Rn

To see any other element in its elemental state,
compounds must be decomposed
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METALS
In their elemental state, metals consist of
billions of atoms bonded together This strong
chemical bonding causes most metals to be solids
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NONMETALS
In their elemental state, most nonmetals consist
of a small number of atoms bonded together, while
a few consist of billions of atoms bonded
together MOLECULE A group of nonmetal atoms
bonded together Molecules weakly attract, so
molecular matter often exists in the gaseous
state, but the molecules may attract each other
enough to form solids or liquids
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7 of the nonmetals that exist as molecules
produce DIATOMIC MOLECULES
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• Some elements have several forms in the elemental
  state
• Oxygen dioxygen (O2) and ozone (O3)
• Carbon diamond, graphite, buckminsterfullerene

ALLOTROPES Different forms of a given element
due to different interatomic bonding
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IONS Atoms can gain or lose electrons ION An
atom with a positive or negative charge because
it has gained or lost electrons
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Lithium (Z 3)
3 Protons 3 Electrons
3 Protons 2 Electrons
Lithium atom
Lithium ion
Li
Li
Li ? Li e-
CATION A positive ion
Cations have the same name as their corresponding
atom Cations are created when metals form
compounds with nonmetals
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Fluorine (Z 9)
9 Protons 9 Electrons
9 Protons 10 Electrons
Fluorine atom
Fluoride ion
F
F-
F e- ? F-
ANION A negative ion
Anions are named with an ide ending Anions are
created when nonmetals form compounds with metals
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Many ion charges can be predicted from the
Periodic Table
barium Ba2
potassium
aluminum
bromide Br-
oxide
phosphide
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REVIEW FOR TEST
46 elemental names and symbols Solid, liquid,
gas Substance, element, compound Heterogeneous,
homgeneous Mixture, solution Physical and
chemical properties Physical and chemical
changes Filtration Distillation
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REVIEW FOR TEST
Energy Specific heat capacity Heat
calculations Scientists and their work Atomic
structure Protons, neutrons, electrons Atomic
number, mass number Isotopes Formulas of
compounds
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REVIEW FOR TEST
Elemental abundances Periodic Table Properties of
metals, nonmetals, metalloids Group names Active
and inert elements Diatomic elements Allotropes Ca
tions and anions Ion charges from the Periodic
Table
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