22
No one knows how many elements are left to discover.
2 elements
There are many reactive elements. They show up more on the upper left of the Periodic Table. Some of these are plutonium, uranium, Mercury and lead.
One.
one
'left' is one syllable.
One
That is correct; the first column on the left contains only elements with one electron in their outer shell, also known as "valance electrons". This column is referred to as Group 1, also known as the Alkali Metals.
there is no such limitation. you can have any number of form elements
Plastics have many elements in them but they may be made of one type of "particle" or "string" of atoms/elements.
there are two elements, hydrogen and oxygen and one atom of each
There are 6 elements; 1,2,3,4,5,&6.