2. periods are
that run from left to right
3. elements in the same period have the same
every element in the first period has
element in the second period has
pattern?
shell for its
for its
every
see the
5. groups are
that run from top to bottom.
6. the elements of a group have the same number of
shell.
in their
7. every element in group one has
element in group two has
electron in its outer shell. every
electrons in its outer shell.
8. hydrogen is special because it can act like two groups,
and
9. hydrogen sometimes is
electron.
an electron and sometimes it has an
electrons in its outer shell, it is grouped
10. although helium has only
with elements that have
elements. they each
11. the green elements on this table are called
have two electrons in their outer shell.