. Which element has the smallest atomic radius? (A) fluorine (B) chlorine (C) bromine (D) iodine (E) astatine Element X has these ionization energies: Ionization Energy First 419 kJ/mol Second 3051 kJ/mol Third 4411 kJ/mol Element X most likely is (A) Ca (B) Si (C) Br (D) K
The Correct Answer and Explanation is:
For the first question:
Which element has the smallest atomic radius?
The correct answer is (A) fluorine.
Explanation:
Atomic radius generally decreases as you move across a period (from left to right) on the periodic table, and it increases as you move down a group (from top to bottom). This is because, as you move across a period, the number of protons in the nucleus increases, which pulls the electrons closer to the nucleus, thereby decreasing the size of the atom. Moving down a group adds more electron shells, making the atomic radius larger.
Among the elements listed — fluorine, chlorine, bromine, iodine, and astatine — fluorine is the smallest because it is at the top of Group 17 (the halogens) and has the fewest electron shells.
For the second question:
Element X has these ionization energies:
- First: 419 kJ/mol
- Second: 3051 kJ/mol
- Third: 4411 kJ/mol
Element X most likely is: (A) Ca (B) Si (C) Br (D) K
The correct answer is (B) Si.
Explanation:
Ionization energy refers to the energy required to remove an electron from an atom. The first ionization energy is usually the lowest, and successive ionization energies increase because it becomes harder to remove electrons as the atom becomes positively charged.
In this case, there is a significant jump in the ionization energies between the first and second ionization energies, which suggests that Element X has two valence electrons (since after the first electron is removed, the next electron is much harder to remove).
- Ca (Calcium) has two valence electrons, but its ionization energies are generally much lower.
- Si (Silicon) also has two valence electrons, and the jump between the first and second ionization energies corresponds well to the given data.
- Br (Bromine) has seven valence electrons, so the first ionization energy would be lower, and the jump would not be as pronounced.
- K (Potassium) has one valence electron, so the second ionization energy would be much higher.
Thus, Silicon (Si) best fits the pattern of ionization energies provided.
