Indicate the substance that contains the smallest cation. (a) BaCl2 ; (b) Al2 O3 ; (c) Mg3 N2 ;

Indicate the substance that contains the smallest cation....

Key Concepts

Ionic Radii

Ionic radii refer to the effective sizes of ions in a crystal lattice. The size is key in determining various properties of ionic compounds, including lattice energy and the packing of ions, and is influenced by both the nuclear charge and the number of electron shells.

Periodic Trends

Periodic trends help predict trends in ionic sizes across the periodic table. Moving across a period, increasing nuclear charge with little added shielding generally results in smaller ionic sizes. This concept is essential in comparing cation sizes among different elements.

Effective Nuclear Charge

Effective nuclear charge is the net positive charge experienced by electrons in an atom or ion. For cations, a higher effective nuclear charge typically results in a smaller ionic radius, since the electrons are drawn closer to the nucleus. This concept is critical when evaluating which cation is smallest in an ionic compound.

Transcript

00:01 Okay, so this is question 11 .10 in chemistry, the science and context at the end of chapter 11.

00:07 So it asks which of the following compounds has the smallest cat ion.

00:13 Okay, so the cat ion, remember, is the positively charged ion.

00:16 So in here our cat ion is ea2 plus.

00:23 Here it's going to be aluminum 3 plus.

00:27 Okay, this one, max.

00:31 Magnesium and this one, strontium 2 plus.

00:37 Okay, so these are the cat ions of these compounds.

00:42 Okay? and if you forgot how to get the cat ions from the chemical compound formula, previous chapters in the book explain that.

00:54 But essentially, so for the example of barium chloride, i know that chlorides like to be, each chloride is a negative.

01:02 So that means that i have to have barium two plus since chloride.

01:08 There's two of them, right? another thing is based on their groups, right? so barium, magnesium, and strontium are all in the group number two.

01:18 So i know that they're all going to be two plus when they become cat ions.

01:23 And magnesium, i'm sorry, aluminum is in group three.

01:26 So it would be three plus.

01:28 Okay.

01:28 And so like i said, these three are all in the same group.

01:34 So actually, you can all compare them based on size with the one at the highest in the periodic table being the smallest.

01:46 Okay.

01:47 So if we go up in the periodic table, this is just group two of the periodic table, right? so if we go up, this is in decreasing size.

01:58 Okay? and so that means that barium is our biggest, and let's see, magnesium is our smallest.

02:04 So we already know it's not going to be this or this.

02:08 So we know that magnesium is the smallest of the cat ions in group two...

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