Atoms and Moleculese

EXAMPLES OF CHEMICAL NAMES OF COMPOUNDS

CHEMICAL FORMULA CHEMICAL NAME CO2 carbon dioxide CO carbon dioxide Co carbon monoxide NaCl sodium chloride CuO copper oxide Ag Br silver bromide K I potassium iodide H Cl hydrogen chloride (hydrochloric acid) NH4 Cl ammonium chloride K OH potassium hydroxide Na OH sodium hydroxide Ca (OH)2 calcium hydroxide Ca S calcium sulphide Na NO3 sodium nitrate H NO3 hydrogen nitrate (nitric acid) Na HCO3 sodium bicarbonate Zn SO4 zinc sulphate Mg CO3 magnesium carbonate Ca SO4 calcium sulphate Cu CO3 copper carbonate Al PO4 aluminium phosphate Fe SO4 iron sulphate Fe CO3 iron carbonate NH4 NO3 ammonium nitrate NH4 HCO3 ammonium bicarbonate H2 SO4 hydrogen sulphate (sulphuric acid) Na2 SO4 sodium sulphate (NH4)2 CO3 ammonium carbonate

Molecular Mass :

It is the sum of the atomic masses of all atoms in a molecule of the substance.

The formula unit mass  is the sum of the atomic masses of all atoms in a formula unit of a compound.  It is used for those substances whose constituent particles are ions.

Na Cl  -   1 x 23  + 1  x  35.5  =  58.5 μ

Mole Concept :

The word mole was introduced by Wilhelm Ostwald around 1896 and it means heap or pile.

Mole is that quantity in number having a mass equal to its atomic or molecular mass in grams. The  number of  particles present  in  1 mole of  any  substance is  fixed,  with  a  value of 6.022 x 10²³ . This is called the Avocado Constant or Avocado Number (represented by N_o)1 mole  =  6.022 x 10²³ in number

Mass of one mole is also fixed. It is equal to its relative atomic or molecular mass in grams. Molar mass of atoms is also known as grain atomic mass. For this ‘μ’ is changed to ‘g’.

Eg. Atomic mass of hydrogen is 1 μ and its gram atomic mass is 1 g.

Chemists need the no. of atoms and molecules while carrying out reactions so, they need mass in grams to the number. Thus, a mole is the chemist’s counting unit.