There are 80 known elements which have at least one stable isotope.
These lines did not correspond to any known elements on Earth.
In this theory all known elements consist out of the four protoelements.
It is unknown how far the periodic table might extend beyond the known 118 elements.
Its atomic number is 1, which makes it the simplest, known element in the entire universe.
No known element has more than 32 electrons in any one shell.
Science has never been able to break down all the known elements.
In 1863 there were 56 known elements with a new element being discovered at a rate of approximately one per year.
Each model is not completely consistent with all the known elements.
His chart included 63 known elements placed in order of atomic weight.