Class XI

electronic configuration - 1s2 2s2 2p6 3s2 3p6 4s2 3d10  
Cr - 1s2 2s2 2p6 3s2 3p6 4s1 3d5
Cu - 1s2 2s2 2p6 3s2 3p6  4s1 3d10  

Moles    =    given mass
                  molar mass   
1 mol =   11gm of Na
              11u of Na          

Strength = mass/ volume of solution

Strength / Molar Mass = mass/ molar mass x volume = Moles/ volume = Molarity

Strength / Molar Mass = Molarity

Molarity =         Moles of solute 

volume of solution in litres

0.1M = 0.1 mol dissolved in 1 L of solution = 1gm of 10 unit molar mass element dissolved in 1 L of solution.
1 M = 1 mol dissolved in 1L of solution = 11gm of Na is dissolved in 1L of solution.

Molality    =        Moles of solute
                     Mass of solvent in Kg

1m = 1 mol dissolved in 1kg of solvent

Normality = No. of gram equivalents of solute/ volume of solution in L

Oxidising agent ( जो दुसरो के इलेक्ट्रान खा जाए ) means which itself gets reduced (electron खाना ) and oxidizes the opponent. 

Reducing agent (जो दुसरो को खाना खिलाये ) means which itself gets oxidised (electron donation) and reduces the opponent.

Oxidising agent = oxidation state decreases (F + A = F-) = Non metals are oxidising agent

Reducing agent = oxidation state increases (Na + A = Na+) = metals are reducing agent

Iron forms two oxidation states = +2, +3 

Fe+2 = ferrous 

Fe+3 = ferric (OXIDISING AGENT)