Why do elements in the same group of the periodic table have similar properties?

• A. They have identical atomic masses.
• B. They have the same number of protons.
• C. They are all metals.
• D. They have the same number of valence electrons.

Answer: (D)

Verified step by step guidance

1. Understand that elements in the same group (vertical column) of the periodic table share similar chemical properties because they have the same number of valence electrons.
2. Recall that valence electrons are the electrons in the outermost shell of an atom and are primarily responsible for chemical bonding and reactivity.
3. Recognize that having the same number of valence electrons means these elements tend to form similar types of bonds and exhibit similar chemical behavior.
4. Note that atomic mass and number of protons differ among elements in the same group, so these are not the reasons for similar properties.
5. Conclude that the key factor for similar properties in a group is the identical number of valence electrons, which governs their chemical characteristics.