Which of the following is the correct method to determine the number of valence electrons in a neutral atom of a main-group element?

• A. Use the period number to determine the number of valence electrons.
• B. Count all the electrons in the atom.
• C. Subtract the atomic number from the mass number of the element.
• D. Count the electrons in the outermost s and p orbitals based on the element's group number in the periodic table.

Answer: (D)

Verified step by step guidance

1. Understand that valence electrons are the electrons in the outermost energy level (shell) of an atom, which are primarily involved in chemical bonding.
2. Recognize that for main-group elements, the valence electrons are found in the outermost s and p orbitals.
3. Use the group number of the element in the periodic table to determine the number of valence electrons: for groups 1 and 2, the valence electrons correspond to the group number; for groups 13 to 18, the valence electrons equal the group number minus 10.
4. Avoid using the period number to determine valence electrons, as the period indicates the principal energy level, not the number of valence electrons.
5. Do not count all electrons or subtract atomic number from mass number, as these methods do not correctly identify valence electrons.