Structure of the atom

Structure of the atom

1. Structure of the nucleus

   • Consists of:
     • Positively charged Protons
       • Atomic number (Z) = no. protons in atom
     • Neutral Neutrons
       • Mass number (A) = no. neutrons in atom (N) + Atomic no.(Z)
     • Protons and neutron together known as nucleons

2. Electrons and charge of an atom

   • In neutral atom no. protons = no. electrons around nucleus
   • Atom becomes charged by gaining/losing electrons
     • Atoms gaining electrons are negatively charged
       • negative ions called anions
     • Atoms losing electrons are positively charged
       • positive ions called cation
   • Atom with charge called ion

3. E.g. Ion Al

   • Atomic no. (Z) = 13
   • Mass no. (A) = 27
   • No. protons (Z)= 13
   • atom had 13 electrons when neutral. but gains 3 electrons to obtain 3+ chare
     • No. electrons =>13-3 = 10 electrons
   • No. neutrons (N) = mass no. (A) - Atomic no. ( Z)
     • 27-13= 14 neutron