Question

How many valence electrons do each of the following elements have? (a) \(\mathrm{C}\) (b) \(S\) (c) \(\mathrm{K}\) (d) I (e) \(\mathrm{B}\)

Short answer

(a) C has 4 valence electrons. (b) S has 6 valence electrons. (c) K has 1 valence electron. (d) I has 7 valence electrons. (e) B has 3 valence electrons.

Step-by-step solution

Determine Valence Electrons for Carbon (\textrm{C})

To determine the number of valence electrons for Carbon (C), look at its position in the periodic table. Carbon is in Group 14, meaning it has 4 valence electrons since the number of valence electrons corresponds to the group number for Groups 1-2 and 13-18.

Determine Valence Electrons for Sulfur (S)

Sulfur (S) is located in Group 16. Elements in Group 16 have 6 valence electrons. Therefore, Sulfur has 6 valence electrons.

Determine Valence Electrons for Potassium (K)

Potassium (K) is in Group 1 of the periodic table. Elements in this group have 1 valence electron. Thus, Potassium has 1 valence electron.

Determine Valence Electrons for Iodine (I)

Iodine (I) is a member of Group 17, which means it has 7 valence electrons because the elements in this group have 7 valence electrons.

Determine Valence Electrons for Boron (B)

Boron (B) can be found in Group 13 of the periodic table. This group's elements have 3 valence electrons. Therefore, Boron has 3 valence electrons.

Key concepts

Understanding the Periodic Table

The periodic table is a fundamental tool for scientists, structuring elements in rows called periods and columns called groups based on their chemical properties. Its layout reflects how the electron configurations shape these properties.

Elements in the same group exhibit similar chemical behaviors because they have the same number of valence electrons, which are the electrons available for bonding in the outer shell. As we move from left to right across a period, each element has one more proton and is typically one electron heavier than the element before it, reflecting a regular pattern in the properties of the elements.

Groups and Periods

The table's vertical columns, known as groups, are especially informative. The group number can provide a quick reference for determining an element's valence electrons for elements in Groups 1-2 and 13-18. For example, Carbon (C) is in Group 14; thus, it has 4 valence electrons. On the other hand, the horizontal rows, or periods, indicate the number of electron shells.

The Significance of Group Numbers

Group numbers are crucial when examining an element's valence electrons. If you look at the Group 1 elements, they have one valence electron that can be easily lost in a chemical reaction, leading to their reactivity. As a result, Potassium (K), from Group 1, has one valence electron.

Moving across the periodic table, Group 17 elements, also known as halogens, have seven valence electrons, making them one electron short of a complete outer shell, which explains their reactivity and tendency to form salts, such as Iodine (I) having 7 valence electrons.

Understanding Group Trends

As you go down a group, elements have more electron shells, but the number of valence electrons remains the same. This consistency allows us to predict the group's chemical reactivity and properties, highlighting why knowing the group number is essential for understanding an element's chemistry.

Electron Configuration and Valence Electrons

Electron configuration describes the arrangement of electrons around the nucleus of an atom. It determines how these electrons are distributed amongst the orbitals and shell levels. Valence electrons are those in the outermost shell, or highest energy level, of an atom and play a pivotal role in chemical reactions and bonding.

The electron configuration of an element gives us a clear picture of these valence electrons. For example, Boron (B) has an electron configuration which ends in 2s² 2p¹. This means it has a total of 3 electrons in its outer shell, making it have 3 valence electrons. Recognizing the pattern in the configuration allows us to determine the number of valence electrons without necessarily memorizing each element's group position.

Practical Tips for Electron Configuration

Remember that the sum of the superscripted numbers in the outermost shell of an atom's electron configuration gives you the number of valence electrons. This method provides an alternative approach to using the group number for finding valence electrons, and understanding it can offer deeper insights into the behavior of atoms during chemical processes.