Use the periodic table to determine each quantity. a. The...

Use the periodic table to determine each quantity.
a. The number of $3 s$ electrons in $\mathrm{Mg}$
b. The number of $3 d$ electrons in $\mathrm{Cr}$
c. The number of $4 d$ electrons in $\mathrm{Y}$
d. The number of $6 p$ electrons in $\mathrm{Pb}$

Key Concepts

Periodic Table

The periodic table is an organized arrangement of the chemical elements, ordered by increasing atomic number. It not only provides the elemental symbols and atomic weights but also displays periodic trends and recurring properties of elements. This organization allows one to predict element characteristics and determine electron configurations based on their positions in groups and periods.

Electron Configuration

Electron configuration describes the distribution of electrons among the various atomic orbitals in an atom. It follows specific rules such as the Aufbau principle, Pauli exclusion principle, and Hund's rule, which help in determining the order in which orbitals are filled and the resulting chemical behavior of the element.

Atomic Orbitals

Atomic orbitals are regions in an atom where there is a high probability of finding electrons. These include s, p, d, and f orbitals, each with unique shapes and energy levels. Understanding the type and number of electrons in each orbital is crucial for predicting chemical properties and bonding.

Quantum Numbers

Quantum numbers are sets of values that describe the unique quantum state of an electron in an atom. They include the principal quantum number, angular momentum quantum number, magnetic quantum number, and spin quantum number. These numbers determine the size, shape, orientation, and spin of the electron orbitals, thereby influencing the electron configuration.

Transcript

00:01 Chapter 3, problem 52 says use the periodic table to determine each quantity.

00:05 The first quantity is the number of 3s electrons and magnesium.

00:10 So let's find magnesium on our periodic table.

00:14 It has atomic number of 12, so it's located here.

00:17 Magnesium is located in the s block and is located in period 3.

00:21 So the number of 3s electrons it takes to get to magnesium would be 1, 2.

00:27 So our answer for magnesium is 2.

00:31 Question b says the number of 3d electrons to get to chromium.

00:36 Let's do the same thing.

00:38 Our d block is located right here on the periodic table.

00:42 And chromium is located in the fourth period.

00:46 Now the d block is slightly different in that if it's in the fourth period, it's actually 3d.

00:51 In the fifth period, we have 4d and et cetera.

00:55 So the number of 3d electrons would look at the number of electrons in the period 4 of the d block.

01:02 So if we're looking for chromium, we notice that it's one, two, three, four electrons to get to chromium.

01:09 However, because the 4s and the 3d energy level are very, very close in energy, electron are going to be pulled out of the 4s orbital and placed into the 3d orbital, as opposed to being into the 4s orbital.

01:27 So instead of having for an electron configuration of chromium 4s2, 2, 3, d4, we don't have that, but instead our electron configuration is 4 as 1, 3d5...

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