Explanation:

- Groups: These are the vertical columns in the Periodic Table. There are 18 groups, and elements within a group have similar chemical properties.

Correct Answer: Groups

- Valence electrons: These are the electrons present in the outermost shell of an atom. They are important for chemical bonding but are not related to the arrangement of the table.

- Periods: These are the horizontal rows in the Periodic Table. There are seven periods in the table.

- Orbitals: These are regions around an atom's nucleus where electrons are likely to be found. The concept of orbitals comes from quantum mechanics and isn't about the table's layout.