Atoms

1. conservation of mass
2. definite proportion

1. Atomicity

   Annotations:

   • the number of atoms constituting  a molecule is known as its atomicity
   1. monoatomic
   2. diatomic
   3. tetra atomic
   4. poly atomic
2. ions

   Annotations:

   • charged species of metals and non metals
   1. anions
      1. -ve
   2. cations
      1. +ve
   3. poly atomic ion
      1. group of ions carrying charge

Annotations:

• chemical formula of a compound  is a symbolic representation of its composition

1. symbol
2. valency

   Annotations:

   • combining power of an element is known as its valency

1. Molecular mass

   Annotations:

   • the molecular mass of a substance is the sum of the atomic masses of all the atoms in a molecule of the substance. eg. molecular mass of WATER atomic mass of Hydrogen=1u                              oxygen=16u therefore, molecular mass of water where there are two atoms of hydrogen and one atom of oxygen is = 2 x 1 + 1 x 16                   =18 u
2. formula unit mass
3. mole concept

   Annotations:

   • one mole of any species is that the quantity in number having a mass equal to its atomic or molecular mass in grams.
   1. Avogadro number

      Annotations:

      • the number of particles present in one mole of any substance is fixed ,with a value of 6.022 x 10 raise to 23