Elements and the Periodic Table

A Brief History….

Ancient Names for the elements Plumbum Natrium Aurum Argentum Hydrargyrum Kalium Ferrum

John Dalton - Atomic Theory

Proposed in 1803:(1) all matter was composed

of small indivisible particles termed atoms,

(2) atoms of a given element possess unique characteristics and weight

(3) three types of atoms exist: simple (elements), compound (simple molecules), and complex (complex molecules).

Symbols for the elements used by Dalton

Dalton’s Symbols

Jons Jacob Berzelius (1779-1848)

Proposed using the first or a second letter for the element symbol.

Modern Element Symbols

Each element has its own symbol. In writing a symbol, we use 1 or 2 letters. The first letter is always capitalized, the

second is not. Some elements kept symbols for Latin or

Greek words. Elements are grouped in the periodic table.

The Periodic Table

The Periodic Table

The periodic table is a system which helps to classify the elements.

In 1735, there were only 13 known elements; in 1850, there were 47; today there are over 100, including several man-made elements.

The Periodic Table (continued)

The periodic table we use today was devised by a Russian scientist named Dmitri Mendeleev in 1869.

Mendeleev’s Periodic Table

Mendeleev’s Periodic Table

Mendeleev’s Periodic Table

Other Attempts…..

Other Attempts…..

Periodic Table Information

A periodic table can tell us many things: Elements are arranged in order of

atomic numbers (number of protons in the nucleus)

Atomic weight or mass of an element (number of protons and neutrons)

Metals and non-metals are separated in the upper right corner by a zigzag line.

Metals and non-metals

Metals

Properties of metals

All solids at room temperature, except mercury (liquid)

Shiny Malleable (bendable) Good conductors of heat and/or electricity Ductile (can be drawn into thin long wires) Most react with acids Located left of the staircase line in the

periodic table.

Non-metals

Properties of non-metals

Most are gases, some are solids, bromine is the only liquid,

Dull Brittle Poor or nonconductors Do not react with acids Located right of the staircase line in

the periodic table.

Metalloids (semi-metals)

Elements that have some properties of metals and some of nonmetals.

Include all elements on either side of the staircase line except AL and At.

Also includes one form of C, called graphite, which is dull and brittle (nonmetal) but is a good conductor of electricity (metal).

Periodic Table Information Horizontal rows are called periods. Vertical columns are called groups or

families (all elements in the same group have similar characteristics).

The group number is the number of electrons in the outside level or orbit of an atom. These are called valence electrons.

The groups on the periodic table have different names:

Group A – Representative elements (1,2,13-18)

Group B – Transition elements (3-12)

Chemical Families (groups)

Group 1 (IA) – alkali metals Group 2 (IIA) – alkaline earth metals Group 17 (VIIA) – halogens Group 18 (VIIIA) – noble gases Rows on the bottom:

Lanthanide seriesActinide series

Chemical Families – Alkali metals

- group 1, IA- Eg. Sodium, lithium

- Show metallic properties

- Highly reactive, especially with water; reactivity increases down the group

- Cs and Fr are the most reactive metals.

Alkaline earth metals

- Group 2, IIA- Eg. Calcium, magnesium

- show metallic properties

- less reactive than alkali metals; reactivity increases down the group

Halogens

- Group 17, VIIA- Eg. Chlorine, fluorine

- show nonmetallic properties

- reactivity decreases going down the group; F is the most reactive nonmetal

- react with metals to produce salts (ionic compounds)

- react with hydrogen to form compounds that dissolve in water to form acids.

Noble Gases

- Group 18, VIIIA- Helium, neon, argon

- show nonmetallic properties

- extremely low chemical reactivity