Main Group Elements: Periodic Trends - Online Tutor, Practice Problems & Exam Prep

• Periodic Trends A include Lattice Energy, Ionization Energy, Electron Affinity, and Electronegativity, all of which increase towards the top right corner of the periodic table.
• A mnemonic for remembering the increase in Periodic Trends A is 'lie', where L, I, E stand for the initial letters of Lattice Energy, Ionization Energy, and Electron Affinity respectively.
• Periodic Trends B, which consist of metallic character and atomic radius, decrease as one moves towards the top right corner of the periodic table.
• The relationship between Trends A and B is inverse; as Trends A increase, Trends B decrease.
• It's important to review earlier chapters or videos on Ionization Energy and Electron Affinity for a deeper understanding, as these concepts can become complex.

Periodic Trends

Now as we move to the top right corner of the periodic table, we'll notice that similar periodic trends can be grouped together. Here we're going to be talking about periodic trends A versus periodic trends B. For periodic trends A, we say the periodic trend starting with Li or E all increase. These include lattice energy, ionization energy, electron affinity, and electronegativity.

Now you might notice that this spells out the word lie. A helpful memory tool to help us remember their periodic trend is when you lie, you make stuff up. So here all the periodic trends that begin with Li or East, when you lie, you make stuff up. They increase as we go to the top right corner of the periodic table. So these are our type A trends.

Type B has to do with metallic character and atomic radius. So think about it, why would I need to make two different periodic trends if they were doing the same thing? If periodic trend A is increasing, that would mean by default periodic trend B would be decreasing. So metallic character and atomic radius decrease as we head towards the top right corner of the periodic table.

Now here just to remember, we've talked about ionization energy and electron affinity as well as the other periodic trends in earlier chapters. If you don't quite remember what those are or you haven't seen those videos, make sure you go back and take a look. So especially ionization energy and electron affinity because they can get kind of complex the further into them that we go. So make sure you review those if you need to.

So just remember we have periodic trend A and periodic trend B. For A, when you lie, you make stuff up. They all increase as we head towards the top right corner. Trends B decrease as we head towards the top right corner.

Main Group Elements: Periodic Trends Example

Here we're told that Group 3 elements tend to have blank atomic radii and blank ionization energies than group 1A elements. So we're looking at group 3A versus group 1A. So here we would say that atomic radius fits under periodic trend type B, so it decreases as we head towards the top right corner. So as we're going towards the right, we would expect our atomic radius to decrease.

So group 3A elements would have smaller or lower atomic radii than group 1A. So that means the answer's either B or C. Then ionization energy fits under periodic Tron trend type A, which increases as we head towards the top right corner of the periodic table. Here we'd expect a group 3/8 to have a higher ionization energy than group 1A.

This would mean that our final answer would have to be choice B.

Rank the following elements in order of increasing lattice energy: S, In, K, Ba and Cl

• A. Ba < In < S < K < Cl
• B. Cl < S < In < K > Ba
• C. Ba < K < In < S < Cl
• D. Cl < In < K < S < Ba
• E. In < Ba < Cl < S < K

Which of the following elements will have the lowest electron affinity?

• A. Cl
• B. K
• C. P
• D. Be
• E. O

For Group 5A elements, the ionization energy decreases going down a group because:

• A. Their atomic masses increases.
• B. The highest number of their valence orbital shell increases.
• C. Their metallic character decreases.
• D. Their electron affinity increases.
• E. The number of neutrons in their nuclei decreases.