As we move across a period of the periodic table, why do the sizes of the transition elements ch

As we move across a period of the periodic table, why do the...

Key Concepts

Effective Nuclear Charge

Effective Nuclear Charge (Z_eff) is the net positive charge experienced by an electron in an atom after accounting for the shielding by inner electrons. As you move across a period, the increasing nuclear charge pulls electrons closer to the nucleus. In transition elements, additional electrons go into inner d orbitals, which do not shield as effectively, but their introduction moderates the increase in Z_eff experienced by outer electrons compared to representative elements, where electrons are added to the p orbitals with less internal electron shielding effects.

Shielding Effect

The shielding effect refers to the reduction in the attractive force between the nucleus and the valence electrons due to the presence of inner-shell electrons. In transition metals, the electrons in d orbitals provide a relatively constant shielding effect. This means that although the nuclear charge increases across the period, the inner electrons do not shield the additional charge as effectively, resulting in a more gradual decrease in atomic size.

Atomic Radius Trends Across Periods

Atomic radius trends describe how the size of atoms generally decreases across a period due to the increasing effective nuclear charge which pulls electrons closer to the nucleus. In representative elements, electrons are added to outer p orbitals, leading to a pronounced decrease in size. In contrast, for transition elements, the added electrons enter the more diffuse inner d orbitals, where their impact due to shielding and penetration effects is less pronounced, contributing to a gradual change in atomic radii.

Orbital Penetration and Electron Distribution

Orbital penetration refers to the extent to which electrons can get close to the nucleus, and it varies with different types of orbitals. For transition metals, d orbitals have less penetration compared to the s and p orbitals found in representative elements. This difference in how electrons are spatially distributed and how they experience the nuclear charge leads to a moderated change in the atomic sizes of transition elements compared to the sharper trends seen in representative elements.

Transcript

0:00 Guys.

00:01 So we are doing from eighty two and chapter seven of chemistry central science.

00:06 So as you move across the period of the period table, why, besides the transition metals changed more gradually than those of the representative elements.

00:13 So here's our para table.

00:15 We have representive elements on the left and on the right.

00:17 Let me just put are so you know, the representative and then we have our d block for transition metals here.

00:23 So don't forget the general set above our of our adam.

00:27 We have positive charge a nucleus with electrons orbiting around it.

00:31 Now, remember, remember that like this, these this electron layer does not feel the same as this electron electron liquor because this one is closer to nucleus.

00:44 So there's positive that nicolas possibly charge your electrons are negatively charged, so it creates an attractive interaction between your electrons and your nucleus.

00:56 However, because you have this shell shell here in the inner shell, you're vaillant shell here doesn't feel the nucleus that strongly because part of the negative truck our job inner shell is canceling out that of the outer shell.

01:15 Well, this is knows you're effective.

01:16 Nuclear charts is the effective is equal two z, which is your atomic number minus the and i'll put an e which is going to be your number of inner shell electrons.

01:35 So when we're looking at a representative, elements were adding electrons to our vet to our valin shell.

01:41 So when we add electron to our surveillance vaillant shell, that's not going to affect our that's not going to like cause any extra shielding like for exams.

01:54 Example who? well, we can ride the the effective for each line.

02:00 So we have one, two, three war five, six, seven, eight like this is dizzy effective across these ah wrote into possible across these columns in the pure periodic table.

02:16 So as as we go from as we go from, let's ay ay to pete to p wanted to pee too.

02:23 Electron configuration where we course finally have an increase in our effective, which is going to pull electrons more closely towards towards the nucleus, including our vaillant show.

02:36 Now her r d block, it's a bit different.

02:39 So our d block we have our four...

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