We have studied that atoms are the smallest particles made up of further sub-atomic particles. An element is made up of several atoms. In this lesson we will learn about elements and their classification.
An element is a pure substance that can not be broken down into two or more simpler substance by chemical processes.
Carbon is an element and it can not be broken down into more simpler forms. It is only made up of carbon atoms.
Chemists use chemical symbols to represent elements. The periodic table consists of the name and symbol of the element together.
Names and symbol of some common elements:-
Element | Symbol |
Calcium | Ca |
Carbon | C |
Hydrogen | H |
Iron | Fe |
Classifying Elements:
Elements are classified on the bases of whether they have metallic or non-metallic properties or are they metalloids ( metalloids have both metallic and non metallic properties ). Also there physical states at room temperature ____ gases , liquids or solids. On the left side of the periodic table all elements are metals, on the right side or elements are non-metals.
States | Metals | Metalloids | Non-metals |
Gases | - | - | Helium (He) |
Liquids | Mercury (Hg) | - | Bromine (Br2) |
Solids | Gold (Au) | Silicon (Si) | Carbon (C) |
Properties of Metal, Non-metals and Metalloids:
Properties | Metals | Metalloids | Non-metals |
Appearance | Shiny | Shiny | Dull |
Physical State | Mostly solids; except mercury | Solids | Gases, volatile liquids or solids |
Melting and Boiling Points | High; except for sodium, potassium and mercury | High | Low; except for carbon and silicon |
Ductility and Malleability | Ductile; can be drawn into wires. Malleable; can be hammered into different shapes. Sonorous; make a ringing sound when struck. | Brittle; easily broken when hammered | Brittle; if solid |
Heat Conductivity | Good | Moderate | Poor; except carbon in the form of graphite and diamond |
Electrical Conductivity | Good | Moderate | Poor; except carbon in the form of graphite |
Atoms and Molecules:
Atoms are the smallest particles of an element that have the chemical properties of that element. Each element consists of only one type of atom. Noble Gases, such as neon exist as individual atoms. They are known as monoatomic elements.
A molecule is a group of two or more atoms that are chemically combined (joined together).
Diatomic molecules are those that are formed by the combination of two atoms. Polyatomic molecules are those that contain three or more atoms.
In the next lesson, we will study about compounds and mixtures.
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