Why is the ionization energy of Ca higher than K, but lower than that of Mg?

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Hello. In this problem, we are told that although Polonium is observed to have a higher ionization energy than bismuth, it is observed to have a lower ionization energy than delirium. And we're asked to explain, we are provided with four possible answers. Answer A states that Polonium has a higher ionization energy than bismuth because it has a more effective nuclear charge answer B states that it is because it has a less effective nuclear charge answer C states that it has a less effective nuclear charge and answer D states it has a more effective nuclear charge answer. A states that on the other hand, Polonium has a lower ionization energy than Tulo due to a weaker shielding effect. Answer B states that it's also due to a weaker shielding effect. Answer C states that it's due a stronger shielding effect as does answer D. So let's begin by understanding what is meant by ionization energy. So ionization energy then is defined as the energy required to remove an electron from a neutral atom in the gaseous state, thereby forming a positively charged ion Cron. When we think about the periodic table, as we go from left to right across the periodic table ionization energy then will increase and the size of the atom will decrease. And there these are due for the same reason. So as we go from left to right, we are adding protons to the nucleus of the atom, we are also adding electrons to balance the charge, the electrons are added to the same energy level. So they are not good at shielding the nucleus. And so each additional electron then sees a higher positive charge. So we refer to that as a larger effective nuclear charge is what the electrons see. This larger effect of nuclear charge then draws the electrons in which then causes the atom to be smaller. If it is smaller, then it is that means then the little electrons are more tightly held to the nucleus, making it harder to remove them, which causes then the ionization energy to increase as we go from left to right. And this is generally true as we go down the periodic table, then the ionization energy decreases and this is due to shielding effect. And so as we go down the periodic table, we are adding protons, we are also adding electrons and those electrons are now being added to higher energy levels. And so the electrons then in the interior are better at shielding the outer electrons from the nuclear charge, which means then that those electrons are less tightly held on the outside. That means then that they'll be easier to remove. And so the ionization energy goes down if we now take a look at the periodic table of elements and the location of polonium, bismuth and Tali. To understand the reason why we see the difference in the ionization in this periodic table, we see the location of bismuth delirium and polonium highlighted in yellow. So from what we stated above, again, the ionization energy in general will increase as we go from left to right cross periodic table. And this is again due to the higher effective nuclear charge and it will decrease as we go down the periodic table and this is due to shielding. So when we look at the location of these elements that tells us then that polonium which is to the right of business will have a greater ionization energy and delirium which is above polonium will have a greater ionization energy going back to our answers. Then we see that first one states that polonium has a higher an organization energy than bismuth because it has more effective nuclear charge. So that is correct. The second part though states on the other hand, polonium has a lower ionization energy than to lori due to a weaker shielding effect. And that's incorrect answer. B states the polonium has a higher ionization energy than bismuth because it has a less effective nuclear charge. This is also what answer C states. So both of these are incorrect answer. D states that polonium has a higher ionization energy than B because it is more effective nuclear charge. And on the other hand, polonium has a lower ionization energy than delirium due to a stronger shielding effect. So that is true for both statements. So the correct answer then is D thanks for watching. Hope this helped.

Why is the ionization energy of Ca higher than K, but lower than that of Mg?

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Key Concepts

Ionization Energy

Periodic Trends

Effective Nuclear Charge