Which of the following sequences correctly places the elements Na, Mg, Al, and Si in order of increasing ionization energy?

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

Answer: (C)

Verified step by step guidance

1. Recall that ionization energy is the energy required to remove an electron from a gaseous atom. Generally, ionization energy increases across a period (left to right) in the periodic table and decreases down a group (top to bottom).
2. Identify the positions of the elements Na, Mg, Al, and Si in the periodic table. They are all in the same period (Period 3), with Na on the far left and Si towards the right.
3. Since ionization energy increases from left to right across a period, the order of increasing ionization energy should start with the element furthest to the left (lowest ionization energy) and end with the element furthest to the right (highest ionization energy).
4. Arrange the elements in order from left to right in Period 3: Na, Mg, Al, Si. This order corresponds to increasing ionization energy because each subsequent element holds its electrons more tightly.
5. Compare the given sequences to this order and identify which one matches the increasing ionization energy trend: Na < Mg < Al < Si.