periodic table

• first 20 elements of the periodic table are.

  -hydrogen -helium -lithium -beryllium -boron -carbon -nitrogen

  -oxygen -fluorine -neon -sodium -magnesium -aluminium

  -silicon -phosphorus -sulfur -chlorine -argon -potassium -calcium
• hydrogen has one proton, no neutrons and one electron.
• atomic number is the number of protons in an atom of an element.
• mass number is the total number of protons and neutrons in an atom of an element.
• symbol for sodium is Na
• mass # for the first 20 elements ?

  1 4 6.9 9 10.8 12 14 16 19 20.2 23 24.3 27 28.1 31 32.1 35.5 40 39.1 40.1
• the symbol for potassium is K and the symbol for sodium is Na