The number of electrons determines an element's position.
The atomic number
The number of valence electrons
You don't: The periodic table is a format for displaying elements, not compounds.
All elements are made up of a single atom. This is the defining characteristic that makes it an element as opposed to a compound.
Because we haven't discovered enough elements to go that far into the orbitals
The f-block elements are placed at the bottom of the periodic table because if they were placed where they belong the periodic table would be too big to fit on a normal sheet of paper.
Dirt is a mixture. Only what appears on the Periodic Table are elements, and as dirt is a combination of many things it has no single chemical composition so it is not a compound.
You don't: The periodic table is a format for displaying elements, not compounds.
It isn't on the periodic table since it is not a single element but a compound made of two elements: hydrogen and chlorine.
All elements are made up of a single atom. This is the defining characteristic that makes it an element as opposed to a compound.
The number of electrons in the atoms outer shell.
The elements on the periodic table are considered to be Baryonic matter. The periodic table does not include dark matter, dark energy, antimatter, or exotic matter. Every single matter can be found in the periodic table of elements.
Because we haven't discovered enough elements to go that far into the orbitals
The size of the membrane pores determines which molecules can pass through.
H2O isn't a single element, which is what the periodic table Most things are made of compounds of these elements. . It is comprised of 2 hydrogen atoms (H, on the periodic table) and oxygen (O, on the periodic table).
Dirt is a mixture. Only what appears on the Periodic Table are elements, and as dirt is a combination of many things it has no single chemical composition so it is not a compound.
With the exception of hydrogen, all elements have an electron cloud, and a nucleus composed of protons and neutrons. Hydrogen has a single proton nucleus orbited by a single electron.
group
The f-block elements are placed at the bottom of the periodic table because if they were placed where they belong the periodic table would be too big to fit on a normal sheet of paper.