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Why is the ionization energy of Ca higher than K, but lower than that of Mg? (4.7)
3. Ionic Compounds
Periodic Trend: Ionization Energy (Simplified)
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Which element from Group 7A has lowest ionization energy.
A
I
B
Br
C
Cl
D
F
E
Ne
Verified step by step guidance1
Identify the elements in Group 7A (also known as Group 17 or the halogens) from the periodic table: Fluorine (F), Chlorine (Cl), Bromine (Br), and Iodine (I). Note that Neon (Ne) is not part of Group 7A; it is a noble gas in Group 8A.
Understand the concept of ionization energy: it is the energy required to remove an electron from an atom in the gaseous state. Generally, ionization energy decreases as you move down a group in the periodic table.
Recall that as you move down Group 7A from Fluorine to Iodine, the atomic size increases. This is because additional electron shells are added, increasing the distance between the nucleus and the outermost electrons.
Recognize that with increased atomic size, the outermost electrons are less tightly held by the nucleus due to increased electron shielding. This results in a lower ionization energy for elements further down the group.
Conclude that among the halogens listed (F, Cl, Br, I), Iodine (I) has the lowest ionization energy because it is the heaviest and largest atom in Group 7A, making it easier to remove an electron compared to the others.
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