The Periodic Table

The most important document

in chemistry

Learning objectives

Define group and period as related to periodic table

Describe properties of metal, semi-metal and nonmetal

Write names and symbols of several common elements

Predict type of element from position in periodic table

Classification of matter

reprise

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

C

Ca

Cl

N

O

Al

P

Common elements and

symbols – less obvious

Sodium

Potassium

Iron

Mercury

Silver

Gold

Tungsten

Na

K

Fe

Hg

Ag

Au

W

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-yet-undiscovered elements and their properties. Predictions often proved astonishingly accurate.

The modern periodic tableThere are 92(91) naturally occurring elements:

2 liquids, 11 gases, 23-25 nonmetals

The Periodic Table: Groups and

PeriodsGroups are columns of

elements

Periods are rows of

elements

The Periodic Table: elements in same

group have similar properties

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: non-metals -insulators (or perhaps semiconductors), poor heat

conductors mostly. Solids are brittle. Several are gases,

one is a liquid.

Transition from metal to

nonmetal

Left to right

along period

Bottom to

top up

group

The Periodic Table: semi-

metals – borderline cases Some properties are

metal-like

Other properties are nonmetal-like

Semiconductors

Compare and contrast

Atoms and ions

Atoms contain electrons (negative charge) and protons (positive charge)

Atoms are neutral: electrons = protons

Ions are charged particles: electrons ≠ protons

Positive ion (cation) has fewer electrons (Mg2+)

Negative ion (anion) has more electrons (N3-)

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

Charges on main group ions

predicted by group number