Arrange the atoms according to decreasing effective nuclear charge experienced by their valence

Arrange the atoms according to decreasing effective nuclear...

Key Concepts

Effective Nuclear Charge (Z_eff)

Effective nuclear charge is the net positive charge experienced by an electron in an atom, taking into account both the actual nuclear charge (the total positive charge from the protons) and the reduction in this charge due to the shielding effect of inner electrons. It is a key factor in determining how strongly electrons are held by the nucleus.

Shielding Effect

The shielding effect occurs when inner electrons partially block the nuclear charge from being fully experienced by outer electrons. This reduction in attractive force means that electrons in higher energy levels experience a lower effective nuclear charge compared to those closer to the nucleus.

Periodic Trends

Periodic trends in effective nuclear charge are observed across the periodic table, where typically, as one moves from left to right across a period, the effective nuclear charge on valence electrons increases due to a rise in the number of protons with minimal additional shielding. These trends influence properties such as atomic size and ionization energy.

Electron Configuration

Electron configuration describes the distribution of electrons among the various orbitals in an atom. The arrangement of electrons, especially the valence electrons, is crucial because it determines the extent of electron-electron repulsions and shielding, which directly affect the effective nuclear charge that these electrons experience.

Transcript

00:01 Chapter 3, problem 68, says, arranged the atoms according to the decreasing effective nuclear charge experienced by their valence electrons.

00:07 The atoms we have are sulfur, magnesium, aluminum, and silicon.

00:22 The atomic numbers for these are 16, 12, 13, and 14, respectively.

00:36 So to demonstrate this, let's use an atom.

00:40 So we're going to have, we're going to do the smallest one, which would be magnesium.

00:45 So we'll have 12 protons in the nucleus.

00:49 The first energy level, we'll have two electrons.

00:56 The second energy level, we'll have eight.

01:11 The third energy level for magnesium and a neutral atom will have two.

01:20 And this will give us a total of 12.

01:24 We have two, four, six, eight, ten, and twelve.

01:30 So this is magnesium.

01:32 The equation for effective nuclear charge is your z effective is equal to the charge of the nucleus minus the charge of the shielding electrons.

01:46 So the charge of our nucleus here for magnesium is 12, and we're going to subtract the number of shielding electrons, which would be 10.

01:53 This is the outer electrons.

01:55 On the outer energy level, the ones that are inside are the core electrons are shielding.

02:00 So that minus 10 would give us two...

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