Elements and the Periodic Table

Elements

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Atoms that are the smallest particles of matter. An atom is the smallest particle of an element that has the properties of that element. Salt is an example made up of the elements sodium and chloride. Water is made up of the elements hydrogen and oxygen.

Many centuries ago, Greek thinkers arrived at a conclusion that every thing like gold, silver, sulfur, dogs, trees and humans were made up of four different materials called elements. These four elements were earth, air, fire and water. Some other thinkers thought that matter was made up of small particles called atoms. The elements theory became more popular.

Atomic Theory

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In 1803 John Dalton carried out a number of experiments with water. Using electricity he tried to split water into its two basic elements hydrogen and oxygen. He found that the two elements had different weights. From his experiments he inferred the following.

1. Atoms of different elements have different weights.

2. Two atoms of the same element are identical.

3. An atom of one element cannot be changed into an atom of a different element.

In the 1700s and 1800s scientists found more and more elements.

As more elements were discovered people began to look for an order.

Periodic Table

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In 1869 Mendeleev studied each of the 63 known elements and grouped them by their properties. This classification is called as Periodic table. Each element shows different properties due to the presence of different atoms present in them.

These elements are classified into different groups based on the similarities in their properties. He grouped all the metals together and non-metals together. He organized his ordered groups in a table, called the periodic table. The table is arranged in rows and columns. Elements in each column are called groups. The elements in each group have similar properties. The elements in each horizontal row are called periods.

Mendeleev left gaps, where none of the known elements could fit. His prediction was that these gaps would be filled at a later stage when new elements were discovered. Today more than 100 elements are listed in the periodic table.

In the periodic table, elements lying to the left of the zigzag line are metals and those lying to the right are non-metals. The elements lying close to the zigzag line exhibit properties of both metals and non-metals.

Metals are hard, malleable, ductile, lustrous, and good conductors of heat and electricity.

Non-metals are dull, non-malleable, and non-ductile elements. They can exist in all three states, solids, liquids, and gases. Non-metals are bad conductors of heat and electricity except graphite.

So far, about 114 elements are known to us, out of which 80 percent are metals and the rest are non-metals.

Books about Elements and the Periodic Table

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Links to other sites on the Periodic Table

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