Elements are made with atoms that have all the same number of protons in their nucleus, their centre. The number of protons in an atom is their atomic number.
There are 118 elements in the periodic table sorted by atomic number. The lightest element is hydrogen consisting of just one proton and one spinning electron.
What is the second lightest element?
Oxygen / Helium / Nitrogen
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Answer to question 1 / Helium.
Helium is the second lightest chemical element with the symbol He and atomic number 2. The more protons an atom has the heavier it is. You might have picked up a piece of lead and noticed how heavy it feels, lead is a chemical element with the symbol Pb and atomic number 82.