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August 23, 2014

Homework Help: Ap Chem

Posted by Emily on Tuesday, January 23, 2007 at 10:51pm.

explain each of the following observations using principles of atomic stucture and/or bonding.
a] potassium has a lower first-ionization engergy than lithium.
b] the ionic radius of N3- is larger than that of O2-.
c] a calcium atom is larger than a zinc atom.
d] boron has a lower first-ionization than beryllium.

a] Both K and Li have relatively low first-ionization energies because they want to get to noble gas configuration. However, Li has more electrons, and therefore, a greater shielding effect. That means that the pull of the electrons by the protons in the nucleus is weaker in Li and it takes less energy to take away outer electrons.

b] Both have the same number of electrons. However, O2- has 8 protons and N3- only has 7. The pull of the electrons by the protons in the nucleus is stronger in O2- because there are more of them, so the ion is pulled tighter and smaller.

c] I'm not positive on this one.

d] Boron has one electron unpaired in the p-subshell and it would like to lose it so it will have all full subshells. Beryllium already has all paired electrons so it takes more energy to pull one away.

Emily. I think you should think this through. Li has fewer electrons than K. since K is much larger than Li, its electron is further from the nucleus; therefore, its ionization potential is lower than that of Li.

b. The nitride ion is larger because there are more electrons in the outer orbit. Since they have the same charge, they repel each other, and the ionic radius increases for the nitride ion over that of oxide ion.

c. hint: look where Ca and Zn are in the periodic table. Remember that the 3d electrons are entering AFTER Ca and leading up to Zn.

d. The answer by Belinda is ok for this one.

Sorry I made a mistake in part a. Li has less electrons so potassium has a higher shielding effect so its proton strength is less and it is easier to remove an electron.

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