5. Substance :
A piece of matter in pure form
Mixture:
Impure matter is called mixture.
Element:
It is substance made up of same type of atoms, having
same atomic number and it can not be decomposed in
to simple substance by ordinary chemical means.
Examples
O2 , H2 etc
6. Substance made up of two or more elements
chemically combine together in a fix ratio by mass.
e.g. NaCl, H2O etc.
7. Mixture
When two or more elements or compounds mix up physically
without any fixed ratio.
Types of Mixture
•Homogeneous :same composition
Examples
ice cream, air, gasoline
9. Atomic number and atomic mass
Atomic number of an element is equal to the proton present in the nucleus of its
atom. It is represented by Z.
Mass number
Mass number is a sum of number of protons and neutrons present in the
nuclease of an atom. It is represented by A.
A= Z+n
n is the number of neutrons
10. Empirical formula
Simplest whole number ratio of atoms present in a
compound.e.g CH is the empirical formula of benzene and
its chemical formula is C6H6.
Molecular formula
Actual number of atoms of each elements present in a
molecule of a compound. Molecular formula derived from
empirical formula e.g. C6H12O6 and its empirical formula is
CH2O
11. Chemical Species:
Ions:
is a atom or group of atom having charge on it. The charge may be positive
or may be negative
Cation :any atom or group of atom having positive charge on it e.g.
12. Anion: Any atom or group of atom having negative charge on it.
13. Molecular Ions:
when a molecule loses or gain an electron it form a molecular ion.
e.g. hydroinum ion
