Contents
What is an Element? and What are the different types of Elements?
Thermochemistry explores the heat changes that occur during chemical reactions, making it an integral part of Chemistry Topics.
A substance which cannot be broken down into two (or more) simpler substances by chemical reactions (by applying heat, light or electricity) is called an element. For example, iron is an element because it cannot be broken down into two or more simpler substances by the usual methods of carrying out chemical reactions such as by applying heat, light or electricity. Please note that the elements themselves are the simplest substances. That is why they cannot be broken down (or split up) into any more simpler substances.
Some of the common elements are : Hydrogen, Helium, Carbon, Nitrogen, Oxygen, Sulphur, Phosphorus, Silicon, Chlorine, Bromine, Iodine, Sodium, Potassium, Magnesium, Calcium, Aluminium, Iron, Zinc, Copper, Silver, Gold and Mercury. Every element is represented by a ‘symbol’. All the elements have separate symbols. No two elements can have the same symbol. A symbol is the short way to write an element. For example, the symbol of Hydrogen is H whereas the symbol of Magnesium is Mg. The symbol of an element also represents ‘one atom’ of that element.
We will discuss the symbols of elements in detail in higher classes.
The smallest particle of an element is called ‘atom’. A sample of an element contains only one kind of atoms. This gives us another definition of element which can be written as : An element is a substance which is made up of only one kind of atoms. There are as many type of atoms as are elements. So, different elements are made up of different kinds of atoms. For example, sulphur element is made up of only sulphur atoms whereas iron element is made up of only iron atoms. The atoms of an element remain unaffected by the physical changes in the element. For example, an atom of liquid sulphur (molten sulphur) or vapour forms of sulphur would be exactly the same as that of solid sulphur. Although there is an enormous variety of substances in the universe but the number of elements forming these substances is limited. There are only 92 naturally occurring elements known to us at present. An important classification of elements is in terms of metals and non-metals. This is discussed below.
Metals And Non-Metals
On the basis of their properties, all the elements can be divided into two main groups : metals and non-metals. Iron, copper and aluminium are examples of metals whereas carbon, oxygen and sulphur are examples of non-metals. All the metals have similar properties. All the non-metals have also similar properties. But the properties of non-metals are opposite to those of metals. Both, metals as well as non-metals are used in our daily life. We also use a large number of compounds of metals and non-metals.
Before we go further and give the characteristics (identifying properties) of metals and non-metals, we should know the meaning of some new terms such as malleable, ductile, brittle and lustrous. Malleable means which can be beaten with a hammer to form thin sheets (without breaking). Ductile means which can be stretched (or drawn) to form thin wires. Brittle means which breaks into pieces on hammering or stretching. Lustrous means shiny (chamakdar). Keeping these points in mind, we will now give the characteristics of metals and non-metals.
Characteristics of Metals
The important characteristics of metals are as follows. Metals are malleable and ductile elements which are good conductors of heat and electricity. Metals are lustrous or shiny. Metals are usually hard and strong. They cannot be cut easily. All the metals are solids except mercury which is a liquid metal. Metals have high melting points and boiling points. Metals have high densities which means they are heavy. Metals are sonorous which means that metals make a ringing sound when we strike them with a hard object.
Some of the examples of metals are : Iron, Copper, Aluminium, Zinc, Silver, Gold, Platinum, Chromium, Sodium, Potassium, Magnesium, Nickel, Cobalt, Tin, Calcium, Lead, Cadmium, Mercury, Antimony, Tungsten, Manganese and Uranium. Out of 92 naturally occurring elements, 70 elements are metals. All these metals are solids except one metal mercury which is a liquid.
Characteristics of Non-Metals
The important characteristics of non-metals are as follows. Non-metals are the elements which are neither malleable nor ductile, they are brittle. Non-metals do not conduct heat and electricity. Non-metals are not lustrous or shiny, they are dull in appearance. Solid non-metals are usually neither hard nor strong. They can be cut easily. Non-metals can be solid, liquid or gases at the room temperature. Non-metals have usually low melting points and boiling points. Non-metals have low densities which means they are light. Non-metals are not sonorous, which means non-metals do not make a ringing sound when we strike them with a hard object.
Some of the examples of non-metals are : Carbon, Sulphur, Phosphorus, Hydrogen, Oxygen, Nitrogen, Fluorine, Chlorine, Bromine, Iodine, Helium, Neon, Argon, Krypton and Xenon. Of the 92 naturally occurring elements, 22 elements are non-metals. Out of these, 10 non-metals are solids, 1 non-metal (bromine) is a liquid whereas the remaining 11 non-metals are gases.
Metalloids
There are some elements which show some properties of metals and the other properties of non-metals. The elements whose properties are intermediate between those of metals and non-metals are known as metalloids. For example, metals are good conductors of electricity whereas non-metals do not conduct electricity at all but metalloids conduct electricity to a small extent. Thus, metalloids are semiconductors. The examples of metalloids are : Silicon, Germanium, Arsenic and Tellurium. We will learn more about metalloids in higher classes. We will now discuss the properties of metals and non-metals in detail.