Practice problem
Check all that apply. Elements in the first row of the periodic table are unique because:
There are only two elements in this row.
They have one electron in their outer shell.
They have a full outer shell of electrons.
They do not have any neutrons.
They have 2 spaces for electrons in their outer shell, rather than 8.
They are radioactive.
Type a concept, like “slope” or “photosynthesis”.
