What is PURE SUBSTANCES and there example

NDA / Chemistry 🧪 Lesson 02 Elements,Mixtures and compounds

PURE SUBSTANCES

These substances have fixed composition and non-variable properties.

These can not be separated into simple substances by physical methods. Elements and compounds are pure

substances. 

1. Elements

An element is a substance which cannot be split up into two or more simpler substances by the usual chemical methods of applying heat, light or electric energy.

There are 118 elements known at present, out of which 92 elements Occur in nature, while remaining 26 elements have been prepared artificially except one.

Elements may be found in all the three forms as solid,liquid or gas.

Elements are divided in the following forms:

(i) Metals The elements which have a tendency to form positive ions by loss of electrons are called metals, e.g. silver, tin, zinc etc. Metals are the elements having lustre, ductility, malleability, conductivity etc. All metals except mercury exists as solids at room temperature. Oxides of metals are basic or amphoteric in nature. Aluminium is

the most abundant metal in the earth's crust.

(ii) Non-metals The elements which have a tendency to form negative ion by gain of electrons are called non-metals. e.g. hydrogen, Oxygen, sulphur etc. They are in solid or gaseous form under normal conditions except bromine which exists as liquid. Oxides of non-metals are neutral (in low Oxidation state) or acidic (in higher oxidation state) in nature.

(iii) Metalloids They are the elements whose properties fall between those of metals and non-metals. e.g. boron (B), silicoon (Si), germanium (Ge), arsenic (As), antimony (Sb),tellurium (Te) and polonium (Po) etc.

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•Elements, compounds and Mistures

•Gas,Solids & Liquids

•Molecules

•Amorphous & crystalline 

•ionic,metallic,covalent & molecular

•Pure substance

•Metal,Non-metal, Metalloids

•Elements