Periodic table                                                        


 1.Hydrogen


Latin name: Hydrogenium
English name: Hydrogen
Year discovered: 1766
Discovered by: Henry Cavendish
Electrons: 1
Protons: 1
Neutrons: 0

Properties :

Atomic number: 1

Atomic weight (Relative atomic mass): 1.0079 (g/mol)
Density: 0.0000899 (g/cm³)
Melting point: -259.1 °C = -434.38 °F = 14.05 K
Boiling point: -252.9 °C = -423.22 °F = 20.25 K
Period: 1
Group: IA
Block: s - block


Definition : hydrogen is chemical element with chemical symbol H and atomic with an atomic weight of 1.007944 hydrogen is the lightest element on the periodic table it's montomic form (H) is most abond and chemical substance in the universe constitutes  roughly 75% of all bbaryonic mass.

2.Helium


Helium
Latin name: Helium
English name: Helium
Year discovered: 1895
Discovered by: Pierre Jules César Janssen, Joseph Norman Lockyer
Electrons: 2
Protons: 2
Neutrons: 2



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