Question

which of the following decreases with increasing atomic number in group 2a?
ionization energy
ionic size
shielding effect
number of electrons

Explanation:

• Ionization energy: As atomic number increases in Group 2A (alkaline earth metals), the number of electron shells increases. The outermost electrons are farther from the nucleus and more shielded. According to the trend, ionization energy (the energy required to remove an electron) decreases down a group.
• Ionic size: Ionic size increases with increasing atomic number in Group 2A because more electron shells are added.
• Shielding effect: Shielding effect increases with increasing atomic number as more inner - shell electrons are present to shield the outermost electrons from the nuclear charge.
• Number of electrons: For Group 2A elements, the number of electrons is equal to the atomic number. So, as atomic number increases, the number of electrons also increases.

Answer:

Ionization energy.