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Basic Concept of Chemistry

⁕ Element
↪ Simple forms of matter which can't be decomposed into simpler substance by any chemical methods are called elements.
Eg: hydrogen, nitrogen, iron, etc.

⁕ Atom

↪ The smallest particle of an element which can take part in chemical reaction can't be broken into smaller unit is called an atom.

⁕ Compound

↪ A compound is a pure substance produced by the combination of two or more elements in definite proportion by weight. It is decomposed into simple substances by suitable chemical reactions.
Eg: Water, CO2, etc.

⁕ Symbol

↪ A symbol is short abbreviation for the full name of an element.
Full name of elements may be Latin, German, English, in honor scientists, planets, etc.

Symbols of a few elements with their Latin names are:

Element Latin name Symbol Element Latin name Symbol
Tin Stannum Sn Sodium Natrium Na
Silver Argentum Ag Potassium Kalium K
Mercury Hydrargyrum Hg Lead Plumbum Pb
Copper Cuprum Cu Antimony Stribium Sb

Symbols of a few familiar elements in honor of the Scientists are:

Element Name of the Scientists Symbol
Mendelevium Mendeleev Md
Nobelium Alfred Nobel No
Fermium Enrico Fermi Fm
Einstenium Albert Einstein Es
Curium Madam Curie Cm

Symbols of some elements from names of planets:

Element Planets Symbol
Uranium Uranus U
Neptunium Neptune Np
Plutonium Pluto Pu

↪ Qualitative Significance of Symbol
⇒ It represents the name of an element.

↪ Quantative Significance of Symbol
 one atom of magnesium element.
⇒ one mole of magnesium.
⇒ one gram atom of magnesium element.
⇒ 24 parts by weight of magnesium.
⇒ 6.023×1023 atoms of magnesium

Some More Terms

⁕ Nucleon

↪ A proton or neutron present inside the nucleus of an atom is called nucleon.

⁕ Atomic number (Z)

↪ It is the total number of protons present in an atom of an element.

⁕ Atomic mass number (A)

↪ It is the total number of proton and neutrons.
Atomic mass number (A) = Total number of p + Total number of n
                                              = Atomic number (Z) + number of n

⁕ Isotopes

↪ Different species of an element having same atomic number but with different atomic mass numbers.

⁕ Atomic Weight

↪ Atomic weight of an element is defined as how many times of an atom of an element is heavier than 1/12th mass of one atom of C-12 isotopes.

Eg: Atomic weight of mg = 24 amu.

⁕ Molecular weight 

↪ Molecular weight of a substance is defined as how many times of a molecules of a substance is heavier than the 1/12th mass of one atom of C-12 isotope. Eg: molecular weight of CO2 = 44 amu.

⁕ Molecule

↪ The smallest particle of substance which is capable of independent existence and possess the properties of that substance during chemical reaction is called molecule.

⁕ Radical

↪ An atom or a group of atoms as an integral fragment of molecule having either positive, negative or no charge is called radical.

⁕ Valency

↪ It is combining capacity of an atom or group of atoms and it is measured as the number of H atoms that one radical can combine to form a molecule.

⁕ Variable Valency

↪ Some elements show two or more than two valency in their compounds. These elements are said to exhibit variable valency. Metal name ends in -ous for lower valency and -ic for higher valency.

⁕ Oxidation state of positive and negative radicals

↪ The positive and negative radicals in solution have their integral identity and called as cation and anion respectively. 
↪ Metals form cations and non-metals form anions. The valency of these radicles when expressed in their charge are termed as oxidation state.

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