Hydrogen H

Atomic Number: 1
Atomic Weight: 1.008

Human Physiology:

• Building block of life
• Simplest element
• Part of H₂O (water) which is essential to life and present in all organics

Prevalence:

• Most plentiful gas in universe
• Makes up 98% of known universe

Sources:

• Water abundant throughout universe
• Heavy water is toxic

Deficiency:

• As part of water can cause dehydration

Excess:

• In theory could asphyxiate by denying 0₂
• Not toxic but highly flammable and explosive