Electropositivity of elements across the periodic table normally

Analyze the question: Electropositivity is the tendency of an atom to lose electrons and form positive ions (metallic character). The question asks how it changes across the periodic table, either down a group or across a period.

Explain the concept:

• Across a period (left to right): Nuclear charge increases while the number of shells stays the same. The outer electrons are pulled in more strongly, atomic radius decreases, and ionisation energy increases. Atoms therefore lose electrons less easily, so electropositivity decreases.
• Down a group: The number of shells increases, so atomic radius grows. The outer electrons are farther from the nucleus and are shielded by inner shells. Ionisation energy falls and electrons are lost more easily, so electropositivity increases.

Solution (checking each option):

• A. Constant down the group: false. It increases down the group.
• B. Increases across the period: false. It decreases.
• C. Decreases across the period: true.
• D. Decreases down the group: false. It increases.

Example: In Period 3, sodium (Na) is highly electropositive, magnesium is less so, and aluminium less still. Chlorine is hardly electropositive at all. Down Group 1, potassium is more reactive and more electropositive than sodium, which is more so than lithium.

Tip: Remember "Across = Atoms Attract more", meaning the nucleus holds electrons tighter, so metallic character and electropositivity drop. Down a group, the opposite happens: metallic character and electropositivity rise.