Atoms, Moles, Formulae and Equations

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Atom is the smallest particle of an element, which can take part in chemical reaction. Molecule is the smallest particle of an element which can exist on its own and still retain the chemical properties of that element.  Ion is an atom or group of atoms which are either positively or negatively charged due to loss or gain of electrons. First 20 elements Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Flourine Neon Sodium Magnesium Aluminum Silicon Phosphorus Sulphur Chlorine Argon Potassium Calcium Relative atomic mass of an element is the number of times the average mass of one atom of an element is greater than one twelfth of the mass of carbon 12. Relative Molecular mass of a compound is the number of times the average mass of one Molecule of the substance is greater than one-twelfth of the mass of carbon 12. Mole One mole of a substance is the amount containing as many elementary entities as the number of atoms in exactly 12 grams of carbon 12.  Note: Avogadro

Elements, compounds and Mixtures

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An element is a substance, which cannot be split into two or more simple form by any known chemical process.
It also means a substance, which cannot be decomposed into simpler substance by ordinary chemical means.
Note: There are 109 known elements, 90 occur naturally while the rest are artificial. Elements can be grouped in the periodic table as reactive elements, transition elements, lanthanide elements, actinide, pure metals etc.
A compound is a substance formed when two or more elements are chemically combined together. it is represented by a formula. eg when hydrogen and oxygen is combined in 2:1 respectively.
A Mixture is a substance that contains two or more compounds which can be separated by physical means. E.g Dissolution of water.
 Features of a Compound
A compound can be represented by a definite chemical formula.
A compound when once formed is not easy to separate. i.e it's composition is fixed.
The constituents element of compounds can only be separated by chemical means.
Compounds are homogenous.

Features of a mixture
  1. It's components can be separated by either physical or mechanical means.
  2. Mixtures are heterogeneous
  3. It's composition varies
  4. Mixtures can not be represented by any molecular or chemical formula like compounds.

Differences between compounds and Mixtures

Compounds
  • They are chemically bond together and cannot be separated by physical means
  • It can be represented by a formula since they are in fixed ratio.
  • The properties differ entirely from that of the constituents element. 
Mixtures
  • They are not chemically bond together and can be separated by physical means
  • It cannot be represented by a formula since they are not in fixed ratio
  • The properties are sum of those of all the individual constituents


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