Basic terms in chemistry

Chemistry

The branch of science in which we study about the composition of matter, properties of matter, changes in matter and facters which govern these changes.

Matter
             Anything which has some mass and occupies some space is known as matter.

  

Substance:

    The pure form of matter, which has homogeneous composition throughout and has uniform properties is known as substance.

Mixture:

    The impure form of matter is known as a Mixture.

Homogeneous mixture

      Mixture which has homogeneous composition throughout is known as homogeneous mixture.

Example: salt in water

Heterogeneous mixture

         Mixture which has no homogeneous composition throughout is known as hetrogenous mixture.

Example: sand in water

Atom
              The smallest particle of matter which is divisible is known as an atom. It has two parts

• nucleus
• orbits/shell

and it has three particles

• proton
• neutron
• electron

Protons and neutrons are present in the nucleus of the atom and electrons are present in orbits/shells of the atom. Atom s neutral species because the number of protons and numbers of electrons is always equal in the atom. The proton carries a positive charge and the neutron carries a negative charge.

Molecule:

             When two or more atoms combine with each other then a molecule is formed. examples: Water, carbon dioxide.

The molecule has two types:

1. Molecule of element
2. Molecule of compounds

 Element:

    Element is the pure form of a substance consisting of only the same types of atoms. examples:  C, Al.

Compound:

             When two or more than two different atoms combine with each other then compounds are formed.

 

Atomic number

                  The number of protons present in the nucleus or the number of electrons present in orbits is known as the atomic number. It is denoted by Z.

Atomic mass

                  The sum of proton and neutron present in the nucleus of an atom is known as atomic mass and it is denoted by A.

ION

           When an atom loses or gains an electron to complete its outermost shell then an atom is converted into an ion. there are two types of ions.

Cation

           It carries a positive charge. It is formed by the loss of electrons from the outermost shell.

      

  Anion

           It carries a negative charge. It is formed by the gain of electrons in the outermost shell.