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)
2B-1 (of 40)
Most Common Elements in :
Earth’s Crust
Solid Earth
Atmosphere
Universe
Oxygen
Silicon
Aluminum
Iron
Nickel
Magnesium
Nitrogen
Oxygen
Argon
Hydrogen
Helium
2B-2
SYMBOLS FOR THE ELEMENTS
Letters symbolize elements
1st Letter – always a capital
2nd Letter – always lower case
Co
Cobalt
CO
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
2B-3
400 BC DEMOCRITUS
Proposed that all matter is composed of indivisible particles
ATOMS – From the Greek Atomos, meaning indivisible
2B-4
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
2B-5
Ethene is C1H2
Ethane is C1H3
DALTON’S 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
2B-6
FORMULAS OF COMPOUNDS
CHEMICAL FORMULA – The representation of a compound or molecule
using elemental symbols
Writing formulas:
1) Each element present is represented by its elemental symbol
2) A right subscript tells the number of atoms of each element
3) Subscripts of “1” are not written
CS2
Na3AsO4
Zn(NO3)2
BaCl2.2H2O
1 carbon atom
2 sulfur atoms
3 sodium atoms
1 arsenic atom
4 oxygen atoms
1 zinc atom
2 nitrogen atoms
6 oxygen atoms
1 barium atom
2 chlorine atoms
4 hydrogen atoms
2 oxygen atoms
2B-7
1897 J.J. THOMSON
Discovered that atoms consist of subatomic particles
ELECTRONS – Negatively charged subatomic particles
2B-8
Thomson Model of the Atom
PROTONS – Positively charged subatomic particles
2B-9
1910 ERNEST RUTHERFORD
Found that the atoms has a small, positively charged core
which contains almost all of the atom’s mass
2B-10
Rutherford Model of the Atom
NUCLEUS – The dense, positive core of the atom that contains protons
2B-11
1932 JAMES CHADWICK
Discovered a third subatomic particle
This subatomic particle was found the in nuclei of atoms
NEUTRONS – Neutral subatomic particles
2B-12
The Nuclear Model of the Atom
Electron
Proton
Neutron
2B-13
Location
Charge
Relative Masses
Around Nucleus
Nucleus
Nucleus
+
0
1
1836
1839
1964 MURRAY GELL-MANN
Proposed that protons and neutrons are made of smaller
particles called QUARKS
2B-14/15
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
2B-16
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
2B-17
Protons
Neutrons
Electrons
1
0
1
1
1
1
1
2
1
Mass Number
1
2
3
Isotope Name
1H
2H
3H
Hydrogen-1
Hydrogen-2
Hydrogen-3
Mass Numbers ARE NOT found on the Periodic Table
2B-18
Protons
Neutrons
Electrons
2
1
2
2
2
2
Mass Number
3
4
Isotope Name
3He
4He
Helium-3
Helium-4
2B-19
Find the number of protons, neutrons, and electrons in each:
Isotope Name
Protons
Neutrons
Electrons
2B-20
27Al
238U
THE PERIODIC TABLE
An arrangement of the chemical elements in order of atomic number, with
elements having similar properties placed in columns
2B-21
1869 DMITRI MENDELEEV
Developed the first periodic table
2B-22
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
2B-23
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
2B-24
NONMETALS
Physical Properties – Opposite of metals
Some are crystalline solids, bromine is a liquid, and some are gases
2B-25
METALLOIDS
Properties of metals and nonmetals
Border the diagonal line separating the metals and nonmetals
2B-26
Hydrogen
Group 1
Group 2
-
A group of its own
Alkali Metals
Alkaline Earth Metals
Group 7
Group 8
Middle Block
Extra Block
-
Halogens
Noble Gases
Transition Metals
Inner Transition Metals (Lanthanides and Actinides)
Cu, Ag, Au, Pt -
2B-27
Noble Metals
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
1) Noble Metals
: Cu, Ag, Au, Pt
2) Noble Gases
: He, Ne, Ar, Kr, Xe, Rn
To see any other element in its elemental state, compounds must be
decomposed
2B-28
METALS
In their elemental state, metals consist of billions of atoms bonded together
This strong chemical bonding causes most metals to be solids
2B-29
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
2B-30
7 of the nonmetals that exist as molecules produce DIATOMIC MOLECULES
2B-31
Some elements have several forms in the elemental state
1) Oxygen : dioxygen (O2) and ozone (O3)
2) Carbon : diamond, graphite, buckminsterfullerene
ALLOTROPES – Different forms of a given element due to different
interatomic bonding
2B-32
IONS
Atoms can gain or lose electrons
ION – An atom with a positive or negative charge because it has gained or
lost electrons
2B-33
Lithium (Z = 3)
3 Protons
3 Electrons
3 Protons
2 Electrons
Lithium atom
Li
Lithium ion
Li+
Li → Li+ + eCATION – A positive ion
Cations have the same name as their corresponding atom
Cations are created when metals form compounds with nonmetals
2B-34
Fluorine (Z = 9)
9 Protons
9 Electrons
9 Protons
10 Electrons
Fluorine atom
F
Fluoride ion
F-
F + e- → FANION – A negative ion
Anions are named with an –ide ending
Anions are created when nonmetals form compounds with metals
2B-35/36
Many ion charges can be predicted from the Periodic Table
barium
potassium
aluminum
oxide
phosphide
Ba2+
bromide
Br-
2B-37
REVIEW FOR TEST
46 elemental names and symbols
Solid, liquid, gas
Substance, element, compound
Heterogeneous, homogeneous
Mixture, solution
Physical and chemical properties
Physical and chemical changes
Filtration
Distillation
2B-38
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
2B-39
REVIEW FOR TEST
Elemental abundances
Periodic Table
Properties of metals, nonmetals, metalloids
Group names
Active and inert elements
Diatomic elements
Allotropes
Cations and anions
Ion charges from the Periodic Table
2B-40