The Periodic Table
The most important document
in chemistry
Learning objectives
 Define group and period as related to
periodic table
 Describe properties of metal, semimetal and nonmetal
 Write names and symbols of several
common elements
 Predict type of element from position in
periodic table
Elements: names and symbols
 All elements have a name and a
symbol (one or two letters)
 Symbols are used in writing compound
formulae and chemical equations
 It is essential to be familiar with both
names and symbols for the important
elements
Common elements and
symbols - obvious
 Carbon
 Calcium
 Chlorine
 Nitrogen
 Oxygen
 Aluminium
 Phosphorous
Common elements and
symbols – less obvious
 Sodium
 Potassium
 Iron
 Mercury
 Silver
 Gold
 Tungsten
1869
Dimitri Mendeleev developed
the periodic table
 Ordered elements according to atomic
weights and physical and chemical
properties.
 Only about 60 elements had been
identified
 Predicted existence of as-yetundiscovered elements and their
properties. Predictions often proved
astonishingly accurate.
The modern periodic table
There are 92 naturally occurring elements: 2
liquids, 11 gases, 23-25 nonmetals
Reduce chemistry of all elements
to discussion of group behaviour
 1A ALKALI METALS: Reactive.
Reactivity increases down group.
Physical properties vary gradually.
 2A ALKALINE EARTH METALS :
Similar to alkalis but less reactive. Lots
of common calcium compounds:
calcium carbonate (limestone, marble),
calcium oxide (lime), calcium sulphate
(gypsum, plaster of Paris)
Important groups on other side
of table
 7A HALOGENS: Very reactive, form lots of
compounds with most elements. Chlorides in
particular are common: NaCl, KCl. Reactivity
decreases down group
 8A RARE, INERT, NOBLE GASES: Discovered
late because of lack of compounds, all gases. Not
“rare” since 1 % argon in air; He second most
abundant element in universe. Very unreactive.
Provide insight into properties of other elements
The Periodic Table: two main
types of element: metals - are
shiny, lustrous; good conductors of
heat and electricity. Only one metal is a
liquid at room temp.
The Periodic Table: nonmetals - insulators (or perhaps
semiconductors), poor heat conductors
mostly. Solids are brittle. Several are
gases, one is a liquid.
The Periodic Table: semimetals – borderline cases
 Some properties are metal-like
 Other properties are nonmetal-like
 Semiconductors
Atoms and ions
 Ions are charged particles with more or
less electrons than protons
 Positive ion (cation) has fewer
electrons
 Negative ion (anion) has more
electrons
Ions and compounds
 Ions are important in one class of
compounds
 Metals form positive ions
 Nonmetals form negative ions
 Periodic table can be used to predict
charges
Rules to predict ion charge
 Cation
 Charge = group number
 Anion
 Charge = - (8 - group number)
 Practice with a few examples