Hydrogen is the most abundant element in the universe. The planet Jupiter is composed mostly of hydrogen., Helium gets its name from helios, the Greek word for the Sun, because it was detected in the Sun many years before it was found on Earth., Lithium has the lowest density of all metals. It can float on water. Lithium gives the red colour to some fireworks., Emeralds are compounds containing beryllium. Some of the oldest emerald mines were developed by the Romans in Egypt 2000 years ago., Before 1808 the only source of boron was from Lake Yamdrok Cho, in Tibet. It is essential for the cell walls of plants., Carbon is found naturally as diamond, graphite and anthracite (a type of coal). Diamond is the hardest known material. Carbon is essential for life and makes up 18.5% of the human body., Nitrogen makes up 78% of the air. Nitrogen is needed to build DNA and amino acids (the building blocks of proteins)., Oxygen makes up 21% of the atmosphere. Living things use oxygen for aerobic respiration., Fluorine is the most reactive of all the non-metal elements., Neon does not react with any other element.,

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