Question

Put the following elements in order of increasing first ionization energy: Ar, Ca, Mg, O, N, At.

A. At < O < N < Mg < Ca < Ar
B. Ar < Ca < Mg < N < O < At
C. At < Mg < Ca < N < O < Ar
D. Ar < Ca < Mg < O < N < At

Answer 1

The order of increasing first ionization energy for the given elements is Ar < Ca < Mg < O < N < At.

Step-by-step explanation:

The first ionization energy is the energy required to remove one electron from an atom in its gaseous state. As we move across a period from left to right, the ionization energy generally increases due to the increasing nuclear charge and decreasing atomic radius. As we move down a group, the ionization energy generally decreases due to the increasing atomic size.

Let's rank the given elements based on their positions in the periodic table:

• Ar (Argon) is in group 18 and period 3
• Ca (Calcium) is in group 2 and period 4
• Mg (Magnesium) is in group 2 and period 3
• O (Oxygen) is in group 16 and period 2
• N (Nitrogen) is in group 15 and period 2
• At (Astatine) is in group 17 and period 6

Based on this information, the correct order of increasing first ionization energy is:

Ar < Ca < Mg < O < N < At

Answer 2

The correct order of increasing first ionization energy Ar < Ca < Mg < O < N < At. This order is based on trends such as atomic size and effective nuclear charge, where elements with smaller atomic size generally have higher ionization energies. The answer is D. Ar < Ca < Mg < O < N < At.

Step-by-step explanation:

Argon (Ar): As a noble gas, argon has a full valence shell, making it more difficult to remove an electron, resulting in higher ionization energy.

Calcium (Ca) and Magnesium (Mg): Both are alkaline earth metals. Magnesium has a smaller atomic size than calcium, so Mg has a slightly higher first ionization energy.

Oxygen (O) and Nitrogen (N): Oxygen has a higher first ionization energy than nitrogen. Both are nonmetals, but oxygen's smaller atomic size leads to a higher ionization energy.

Astatine (At): Astatine is a halogen with the highest first ionization energy among the given elements due to its larger atomic size compared to the others.

Therefore, the correct order is Ar < Ca < Mg < O < N < At, corresponding to option D.