Atomic Structure

Atomic Structure

1. Atom

   • It is the smallest particle of matter capable of taking part in chemical reactions
   • Molecules
     • Group of atoms combined through covalent bond
     • Homoatomic molecule
       • If a molecule consists of similar atoms
     • Heteroatomic molecule
       • If a molecule consists of dissimilar atoms
   • It's made of three sub-atomic particles
     • Protons ( p )
       • Its mass is 1 , and its charge is +1
     • Neutrons ( n )
       • Its mass is 1 , and its charge is 0
     • Electrons ( e- )
       • Its mass is 1/1840 ( negligible ) , and its charge is -1
   • An atom is electrically neutral
     • Number of positively charged protons = Number of the negatively charged electrons
   • Spherical in shape

2. Periodic Table

   • The orderly arrangement of elements in the form of a table , where elements are arranged according to increasing order of atomic number
   • Horizontal rows called periods . Period number = Number of shells
   • Vertical columns called groups . Group number = Number of electrons in the valence shell
   • Group 1, 2 and 3 are metals
   • Group 4, 5, 6, 7 and 8 are non - metals
   • Group 8 / 0 are called noble gases / inert gases
   • Proton number / Atomic number
     • It is the number of protons ( and electrons ) present inside a neutral atom. It's represented by Z. It identifies elements .
   • Nucleon number / Atomic mass
     • It is the sum of protons and neutrons in the nucleus of an atom . It is represented by A

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