Problem 93 - Chemistry Matter and Change

Question

For an atom of tin in the ground state, write the electron configuration using noble-gas notation, and draw its electron-dot structure.

Step-by-Step Solution

Answer

The electron configuration of a ground-state tin atom using noble gas notation is \([Kr] 5s^2 4d^{10} 5p^2\). The electron-dot structure of tin is: . Sn•——• . Where the dots around the Sn symbol represent the 4 valence electrons.

Step 1: Find the noble gas that comes before tin on the periodic table

First, let's find the atomic number of tin (Sn). Tin has an atomic number of 50. Now, we will look for the noble gas that comes before tin in the periodic table. The noble gas that comes before tin (50) is krypton (Kr), which has an atomic number of 36.

Step 2: Write the electron configuration of tin using noble gas notation

Now we will write the electron configuration of tin using noble gas notation. Since the noble gas before tin is krypton, we will start with the electron configuration of krypton and then add the electron configuration for the remaining 14 electrons (50 - 36 = 14). Krypton's electron configuration is [Kr]: \([1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6]\) Now, let's add the electron configuration for the remaining 14 electrons: 5s2: 2 electrons 4d10: 10 electrons 5p2: 2 electrons The electron configuration of tin using noble gas notation is: \([Kr] 5s^2 4d^{10} 5p^2\)

Step 3: Draw the electron-dot structure of tin

To draw the electron-dot structure, we need to focus on the valence electrons of tin. Tin's valence electrons are in the 5s and 5p orbitals, with 2 electrons in each, a total of 4 valence electrons. The electron-dot structure will include the symbol "Sn" (for tin) at the center and four electrons (dots) around it, representing the valence electrons. Since the 5p orbital can hold up to 6 electrons, in tin, there are two unpaired electrons in the 5p orbitals. So the electron-dot structure will be like: . Sn•——• . Here, the dots around the Sn represent the valence electrons of tin in the ground state.

Key Concepts

Noble Gas Notation

Understanding the electron configuration of an element is crucial for studying its chemical behavior. One convenient way to express the electron configuration is through noble gas notation. This approach simplifies the notation by starting with the electron configuration of the nearest noble gas preceding the element in question. The noble gas is denoted by its elemental symbol in square brackets, followed by the additional electron configuration of the chosen element.

For instance, as we saw in the textbook solution for tin (Sn), the noble gas preceding it is krypton (Kr), with an atomic number of 36. Tin has an atomic number of 50, so we first write the noble gas symbol [Kr], then we add the configuration of the remaining electrons, which for tin is: [Kr] 5s^2 4d^{10} 5p^2. Here, we skipped writing out the full electron configuration up to krypton and jumped straight to the electrons that are added after it, making the notation much more manageable.

Electron-Dot Structure

The electron-dot structure, also known as Lewis dot structure, is a graphical representation of the valence electrons in an atom. This depiction is particularly helpful when considering bonding potential and predicting molecular geometry. Valence electrons are shown as dots surrounding the elemental symbol. Paired and unpaired electrons can be indicated, which gives insights into the elements' potential to form bonds.

In our textbook example with tin, the electron-dot structure is especially simplistic since we only have to account for its four valence electrons. With the symbol 'Sn' in the center, surrounded by four dots, we effectively communicate that tin has two unpaired electrons in its 5p orbital, indicating a tendency to form bonds and complete its octet.

Valence Electrons

When it comes to chemical bonding and reactions, the valence electrons play the most critical role. These are the electrons that are found in the outermost shell of an atom and are therefore easily accessible for bonding. The number of valence electrons determines an element's chemical properties and its group in the periodic table. For example, all elements in group 18 have eight valence electrons, making them very stable and mostly inert.

For tin (Sn), the number of valence electrons is four, which is derived from the electron configuration [Kr] 5s^2 4d^{10} 5p^2. The 5s and 5p orbitals are the outermost ones for tin, and they contain the valence electrons. Knowing that tin has four valence electrons helps us to understand that it can make up to four bonds, as it could share or transfer these electrons in interactions with other atoms.