Lesson 3 - The Periodic Table of Elements

Dmitri Mendeleev

The "father" of the periodic table, the work of many scientists contributed to its present form.

In the beginning

Elements gold, silver, copper, tin, lead and mercury have been known.

1869 – a total of 63 elements had been discovered

As the number of known elements grew, scientists began to recognize patterns in properties and began to develop classification schemes.

Hennig Brand (1649)

first scientific discovery of an element (Phosphorus)

Dobereiner (1829)

He proposed the Law of Triads.

Middle element in the triad had atomic weight that was the average of other two members and its properties are also the intermediate between the other two.

Law of Octaves

When the elements are arranged in order of increasing atomic mass, every eighth element has properties similar to the first.

Examples:

Hydrogen, Lithium (first element), Beryllium, Boron, Carbon, Nitrogen, Oxygen, Fluorine (8th element that shows similarity to hydrogen).

The Modern Periodic Table

It is an arrangement of elements in order of their increasing atomic number.

Modern Periodic Law

The physical and chemical properties of elements are periodic functions of their atomic numbers.

When elements are arranged according to increasing atomic number, there is a periodic repetition of their physical and chemical properties.

Atomic Radius (Periodic Trends)

Increases from left to right, Increases from top to bottom

Metallic Property (Periodic Trends)

Decreases as you go from left to right of the periodic table of elements.

Increases from top to bottom.

Electronegativity (Periodic Trends)

The tendency of an atom to attract electron to itself.

Increases as you go from left to right of the periodic table of elements.

 Decreases from top to bottom.

Electron Affinity (Periodic Trends)

The amount of energy released when an electron is added to a neutral atom to form a negatively charged particle.

• Increases from left to right

• Decreases from top to bottom

Ionization Energy (Periodic Trends)

The amount of energy required to remove an electron from an atom.

• Increases from left to right.

• Decreases from top to bottom.

Common Useful Elements

Some elements, especially metals, are used as is to strengthen materials.

Chromium improves hardness and toughness of materials.

Manganese increases toughness and strength.

Group 1A Elements

Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (CS)

Group 2A Elements

Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), Radium (Ra)

Group 3A Elements

Boron (B), Aluminum (Al), Gallium (Ga), Indium (In)

Group 4A Elements

Carbon (Graphite), Carbon (Diamond), Silicon (Si), Germanium (Ge), Tin (Sn), Lead (Pb)

Group 5A Elements

Nitrogen (N2), White and Red Phosphorus (P), 25Arsenic (As), Antimony (Sb), Bismuth (Bi)

Group 6A Elements

Sulfur (Sg), Selenium (Seg), Tellurium (Te)

Harmful Elements

Arsenic, Lead, Mercury, Beryllium