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ELEMENT CLASSES
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📚 Some Basic Concepts of Chemistry 📚

Matter:
Anything that exhibits inertia is called matter. The quantity of matter is its mass.

Classification of Matter:-
Based on chemical composition of various substances.

📍Elements:
➖It is the simplest form of the matter.
➖Smallest unit of an element is known as atom.
➖Total number of the known elements is 118 out of which 98 elements occur naturally and 20 are formed by artificial transmutation.
➖Examples: Na, K, Mg. Al, Si, P, C, F, Br etc.

📍Compound:
➖It is a non-elemental pure compound.
➖Formed by chemical combination of two or more atoms of different elements in a fixed ratio.
➖Examples: H2O, CO2, C6H12O6 etc.

📍Mixture:
➖Formed by physical combination of two or more pure substances in any ratio.
➖Chemical identity of the pure components remains maintained in mixtures.
➖Homogeneous mixtures are those whose composition for each part remains constant.
➖Example, Aqueous and gaseous solution.
➖Heterogeneous mixtures are those whose composition may vary for each and every part.
➖Example, Soil and concrete mixtures.

ELEMENT CLASSES

🧩Dalton’s Atomic Theory:
➖Every matter consists of indivisible atoms.
➖Atoms can neither be created nor destroyed.
➖Atoms of a given element are identical in properties
➖ Atoms of different elements differ in properties.
➖Atoms of different elements combine in a fixed ratio to form molecule of a compound.

🧩Precision and Accuracy:
➖Precision: Closeness of outcomes of different measurements taken for the same quantity.
➖Accuracy: Agreement of experimental value to the true value

🧩Laws of Chemical Combination:
➖Law of conservation of mass:
“For any chemical change total mass of active reactants are always equal to the mass of the product formed”

➖Law of constant proportions:
“A chemical compound always contains same elements in definite proportion by mass and it does not depend on the source of compound”.

➖Law of multiple proportions:
“When two elements combine to form two or more than two different compounds then the different masses of one element B which combine with fixed mass of the other element bear a simple ratio to one another”

➖Law of reciprocal proportion:
“ If two elements B and C react with the same mass of a third element (A), the ratio in which they do so will be the same or simple multiple if B and C reacts with each other”.

➖Gay Lussac’s law of combining volumes:
“At given temperature and pressure the volumes of all gaseous reactants and products bear a simple whole number ratio to each other”.

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By S.S.Srijan

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