The tendency of formation of basic oxide _____ when we are shifting down in a group.

The correct answer is increases.Key Points

• A basic oxide is formed when an element combines with oxygen and produces a basic solution when dissolved in water. 
• The trend of basic oxide formation in a group is dependent on the size of the atom and its valence electrons.
• As we move down a group, the atomic size increases, and the valence electrons are located farther from the nucleus.
• The increase in atomic size and distance of valence electrons from the nucleus leads to a decrease in the effective nuclear charge experienced by the valence electrons.
• As a result, the valence electrons are less strongly attracted to the nucleus, making it easier for them to form a basic oxide.

Additional Information

• The atomic number increases moving left to right across a period and subsequently so does the effective nuclear charge.
• As a result, the atomic radii decrease and the nucleus exerts a stronger attraction on the outside electrons as one moves from left to right across a period.
• The number of full electron shells rises as one moves down a group in the periodic table.
• The orbitals of valence electrons in a group are now farther from the nucleus, but they still have the same effective nuclear charge.
• The atomic radii are therefore larger and the nucleus exerts less force on the outside electrons.