Problem 50 - Chemistry for Allied Health

Question

How many valence electrons are in each element? a. K b. P c. F d. \(\mathrm{S}\) e. \(\mathrm{Li}\) f. B

Step-by-Step Solution

Answer

K: 1; P: 5; F: 7; S: 6; Li: 1; B: 3.

Step 1: Identify the Group Number

Elements in the same group in the periodic table have the same number of valence electrons. The group number can help determine the number of valence electrons for elements in groups 1, 2, and 13 to 18.

Step 2: Determine Valence Electrons for Potassium (K)

Potassium (K) is in group 1 of the periodic table, meaning it has 1 valence electron.

Step 3: Determine Valence Electrons for Phosphorus (P)

Phosphorus (P) is in group 15. Elements in group 15 have 5 valence electrons.

Step 4: Determine Valence Electrons for Fluorine (F)

Fluorine (F) is in group 17, which means it has 7 valence electrons.

Step 5: Determine Valence Electrons for Sulfur (S)

Sulfur (S) is located in group 16. This group has 6 valence electrons.

Step 6: Determine Valence Electrons for Lithium (Li)

Lithium (Li) belongs to group 1, so it has 1 valence electron.

Step 7: Determine Valence Electrons for Boron (B)

Boron (B) is in group 13, giving it 3 valence electrons.

Key Concepts

Periodic Table Groups

The periodic table is organized into vertical columns known as groups. Each group contains elements that share certain chemical properties. One striking feature is that elements within the same group have the same number of valence electrons. These are the electrons present in the outermost shell and are crucial in determining chemical bonding behaviors.
Elements in Groups 1 to 2 and 13 to 18 specifically share this pattern, making it easier to predict their valence electrons just by looking at the group number:

• Group 1: 1 valence electron
• Group 2: 2 valence electrons
• Group 13: 3 valence electrons
• Up to Group 18: 8 valence electrons (except Group 18 which usually has 8 but technically varies due to noble gases)

This simple pattern helps quickly identify an element's reactivity and chemical properties. For example, Group 1 elements like Potassium (K) and Lithium (Li) each have 1 valence electron, making them highly reactive.

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's electron shells and subshells. The way electrons are arranged in these layers affects an element's chemical behavior.
To write an element's electron configuration, it's important to understand the order of energy levels and electrons:

• Electrons are filled into orbitals following the sequence of increasing energy, commonly known as the Aufbau Principle.
• Pauli Exclusion Principle states that an orbital can hold a maximum of only two electrons with opposite spins.
• Hund's Rule suggests that every orbital in a subshell is singly occupied before any orbital is doubly occupied.

Take Phosphorus (P), for example. Its electron configuration is 1s² 2s² 2p⁶ 3s² 3p³. The outer shell, 3p, contains 3 electrons, which correspond directly to its reactive capacity and participation in chemical bonding.

Element Groups

Element groups in the periodic table are collections of elements with similar properties. These groups not just share chemical properties, but often similar physical characteristics as well.
For instance:

• Alkali Metals (Group 1): Include Lithium (Li) and Potassium (K). These elements are soft, highly reactive metals with low melting points.
• Halogens (Group 17): Includes Fluorine (F). These are reactive nonmetals famous for forming salts with metals.
• Chalcogens (Group 16): Include Sulfur (S). Known for varying oxidation states and forming acidic compounds.

These classifications offer a simplified way to predict an element's behavior in reactions. When looking at Boron (B), which resides in Group 13, it's notable for its ability to form covalent bonds easily, showcasing unique properties compared to metals or nonmetals.