This is a period table of elements comprising seven rose designated as periods, and eighteen vertical columns called groups. There are sixteen groups in total, which includes seven main groups, seven sub groups, one group aid and one group zero. Currently, one hundred and eighteen elements have been discovered or synthesized. Ed element number one is hydrogen with a relative atomic mass of one point zero zero eight. Its common baLances are plus one and minus one. Hydrogen gas composed of the element is the least stance and lighter substance. And IT has three isotopes, radium deteriora, tritium. Element number two is helium, with a relative atomic mass of four point zero zero three. This element is a noble gas that generally does not react with other substances. Its common violence is zero, and this is the most difficult substance to liquor. Fy element number three is lithium with a relative atomic mass of six point nine four one, its common violence is plus one, and IT is chemically reactive. Element number four is barillon with a relative atomic mass of nine point zero one two, its common baLance is plus two, and IT is the newest alcove earth metal element. Element number five is born with a relative atomic mass of ten point eight one. Its common violence is plus three, is elemental form, is a non metal whose hardness is second only to diamond. Element number six is carbon with a relative atomic mass of twelve point zero one. Its common baLances in inorganic compounds are plus two and plus four. Its elemental form diamond is the hardest st. Substance and also the most abundant non metal element in the dry wait of cells. Element number seven is nitrogen with a relative atomic mass of fourteen point zero one. Its common baLances are minus three, plus one, plus two, plus three, plus four and plus five. IT is the most abundant non metal element in the air. Element number eight is oxygen with a relative atomic mass of sixteen point zero zero. Its common baLances are minus two and minus one. IT is the most abundant element in the earth's crust and the most abundant element in living organisms serving as the source of human life. Element number nine is flooring with a relative atomic mass of nineteen point zero zero. Its common violence is minus one. IT is the most reactive non metal, and its elemental form cannot be oxidized. Element number ten is non with a relative atomic mass of twenty point one eight. This element is a noble gas that generally does not react with other substances. Its common baLance is zero. Element number eleven is sodium with a relative atomic mass of twenty two point nine nine. Its common violence is plus one IT is very reactive and react vigorously upon contact with their or water and can only be stored in carousing or under rare gases. Element number twelve is magnesium, with a relative atomic mass of twenty four point three one. Its common violence is plus two. IT is one of the common light metals. Element number thirteen is aluminum, with a relative atomic mass of twenty six point nine eight. Its common violence is plus three. IT is one of the common light metals and the most abundant metal in the earth's crust. Element number fourteen is silicon, with a relative atomic mass of twenty eight point zero nine. Its common violence are plus four and minus four. IT is the second most abandoned element in the earth's crust. After oxygen element number fifteen is fast for us with a relative atomic mass of thirty point nine seven. Its common baLances are minus three, plus three in, plus five. Its most common electrode es are red fast for us, and White forests. Red Foster rs can be used to make matches and fireworks. White forest forest is highly toxic and can spontaneously ignite at room temperature as scene in will. All the whisps element number sixteen is sulfur with a relative atomic mass of thirty two point zero six. Its common baLances are plus four, plus six in minus two. IT is relatively soft and light. Its reaction with oxygen to form toxic sofa dioxide is a major source of acid rain element number seventeen is choring with a relative atomic mass of thirty five point four five. Its common baLances are minus one, plus one, plus three, plus four, plus five and plus seven. Its elemental form is very reactive and highly toxic. Element number eighteen is are gone with a relative atomic mass of thirty nine point nine five. This element is a noble gas that generally does not react with other substances. Its common violence is zero. Element number nineteen is patta im, with a relative atomic mass of thirty nine point zero zero. Its common violence is plus one. IT is a metal even more reactive than sodium. Element number twenty is calcium, with a relative atomic mass of forty point zero eight. Its common violence is plus two. This element is a major component of bones.