For each of the following groups, place the atoms and/or...

For each of the following groups, place the atoms and/or ions in order of decreasing size. a. $\mathrm{V}, \mathrm{V}^{2+}, \mathrm{V}^{3+}, \mathrm{V}^{5+}$ b. $\mathrm{Na}^{+}, \mathrm{K}^{+}, \mathrm{Rb}^{+}, \mathrm{Cs}^{+}$ c. $\mathrm{Te}^{2-}, \mathrm{I}^{-}, \mathrm{Cs}^{+}, \mathrm{Ba}^{2+}$ d. $P, P, P^{2}, P^{3}$ e. $\mathrm{O}^{2-}, \mathrm{S}^{2-}, \mathrm{Se}^{2-}, \mathrm{Te}^{2-}$

For each of the following groups, place the atoms and/or ions in order of decreasing size.
a. $\mathrm{V}, \mathrm{V}^{2+}, \mathrm{V}^{3+}, \mathrm{V}^{5+}$
b. $\mathrm{Na}^{+}, \mathrm{K}^{+}, \mathrm{Rb}^{+}, \mathrm{Cs}^{+}$
c. $\mathrm{Te}^{2-}, \mathrm{I}^{-}, \mathrm{Cs}^{+}, \mathrm{Ba}^{2+}$
d. $P, P, P^{2}, P^{3}$
e. $\mathrm{O}^{2-}, \mathrm{S}^{2-}, \mathrm{Se}^{2-}, \mathrm{Te}^{2-}$

Key Concepts

Periodic Trends

Periodic trends describe how atomic and ionic sizes change in a predictable way across periods and down groups in the periodic table. Generally, atomic radii decrease across a period due to increasing effective nuclear charge, and increase down a group as additional electron shells are added.

Effective Nuclear Charge

Effective nuclear charge is the net positive charge experienced by an electron in an atom or ion after accounting for shielding by other electrons. A higher effective nuclear charge generally pulls the electrons closer to the nucleus, resulting in a smaller atomic or ionic radius.

Ionic Charge Effects

Ionic charge effects refer to how the gain or loss of electrons influences an ion's size. Cations, which form by losing electrons, are typically smaller than their neutral atoms due to reduced electron-electron repulsion, while anions, which gain electrons, are larger because the additional electrons increase repulsive forces and spread out the electron cloud.

Isoelectronic Comparisons

Isoelectronic species are atoms or ions that have the same number of electrons. When comparing isoelectronic species, differences in the nuclear charge dictate their sizes: species with a higher nuclear charge tend to have smaller radii, as the electrons are more strongly attracted to the nucleus.

Electron-Electron Repulsion and Nuclear Attraction

The overall size of atoms and ions is determined by the balance between the attractive force of the nucleus on the electrons and the repulsive forces between electrons. Variations in electron count and the net positive charge of the nucleus alter this balance, leading to differences in atomic and ionic radii.

Transcript

00:02 Okay, so when we're looking at the size of ions, over here, so the size of ions, there's a couple rules that we want to follow.

00:15 The first one, if we look at the periodic table, love my drawings, the columns, as you go up and down the columns, so these different columns here, so we have those ones, we have kind of these metals there, and we have these fun ones over here, okay? so we have all these different groups, okay? and what they've actually found that as you go down a group, the size will increase.

00:46 Okay, so here's one rule here.

00:48 So as you go down a group, the size increases.

00:56 Okay.

00:57 Another rule that you can follow, i'm going to do this one.

01:00 Let's do it in red, is we can look at the atomic number, okay? and so the atomic number, the atomic charge of the ion.

01:10 Okay.

01:11 Or atom, whatever we're looking at, they reframe this as z.

01:16 So z, which is the atomic charge.

01:23 If as the atomic charges increases, size decreases.

01:31 So that's the second rule.

01:32 The third rule that you can look at is we know that cations.

01:40 So cations, when they have an overall positive charge versus you have anion that have.

01:47 A negative charge.

01:49 Catoids are generally larger in size than anions.

01:55 So anions are smaller than cat ions.

02:00 Or sorry, let me rephrase that.

02:04 Okay, so rephrasing that and i need to erase that.

02:09 Anions are larger than cat ions.

02:13 Okay.

02:13 So anions, they have a more negative charge and those extra electrons there, kind of repulse and stuff, making it a larger.

02:21 Atom, okay? or a larger ion is what that would end up being.

02:26 And so if we were looking at this, let's look at some examples here.

02:29 So let's say, for example, that i have lithium, which has a positive, with a positive, sodium with a positive, rb with a positive, and with a positive.

02:46 So if we look at the periodic table, we can notice, let's look and see which one of these rules we can follow.

02:51 Here.

02:52 And if we notice there, we have lithium, sodium, potassium, rubidium, and cesium, they are all in the same group.

02:59 And they're also, they're all in this first column there...

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