Arrange the following elements in order of increasing first ionization energy: Na, Mg, Al, Si.

• A. Na < Mg < Al < Si
• B. Si < Al < Mg < Na
• C. Al < Si < Na < Mg
• D. Mg < Na < Si < Al

Answer: (A)

Verified step by step guidance

1. Recall that the first ionization energy is the energy required to remove one mole of electrons from one mole of gaseous atoms, and it generally increases across a period from left to right in the periodic table due to increasing nuclear charge and decreasing atomic radius.
2. Identify the position of each element (Na, Mg, Al, Si) in the periodic table. All four elements are in the same period (Period 3), with Na on the far left and Si more to the right.
3. Understand that as you move from Na to Si across the period, the nuclear charge increases, which tends to increase the ionization energy because electrons are held more tightly by the nucleus.
4. Consider any exceptions or electron configurations that might affect ionization energy. For example, Al has a 3p electron which is slightly easier to remove than the 3s electrons in Mg, so Al's ionization energy is slightly less than Mg's despite being to the right.
5. Based on these trends and exceptions, arrange the elements in order of increasing first ionization energy: start with the element with the lowest ionization energy (Na), then Mg, then Al, and finally Si with the highest ionization energy.