Question

Determine the valence level and the number of valence electrons for each of the following elements. (a) \(\mathrm{Al}\) (b) \(\mathrm{S}\) (c) As

Short answer

The valence level and valence electrons for each of these elements are as follows: For \( \mathrm{Al} \), the valence level is 3 and the number of valence electrons is 3. For \( \mathrm{S} \), the valence level is 3 and the number of valence electrons is 6. For \( \mathrm{As} \), the valence level is 4 and the number of valence electrons is 5.

Step-by-step solution

Determine valence level and electrons for Aluminum (Al)

Aluminum is located in the 3rd period and the 13th group in the Periodic Table. According to the Periodic Table, elements in Group 13 have 3 valence electrons and the period number signifies the valence level. So for \( \mathrm{Al} \), the valence level is 3 and the number of valence electrons is 3.

Determine valence level and electrons for Sulfur (S)

Sulfur is located in the 3rd period and the 16th group in the Periodic Table. Elements in Group 16 have 6 valence electrons and the period number signifies the electron shell. So for \( \mathrm{S} \), the valence level is 3 and the number of valence electrons it has is 6.

Determine valence level and electrons for Arsenic (As)

Arsenic is located in the 4th period and the 15th group on the Periodic Table. Elements in Group 15 have 5 valence electrons and the period number determines the level. So for \( \mathrm{As} \), the valence level is 4 and the number of valence electrons it has is 5.

Key concepts

The Periodic Table

The Periodic Table is the Rosetta Stone of chemistry, providing a systematic way to categorize and predict the properties of elements. Imagine a library organized in such a way that you could infer the genre, plot, and complexity of each book simply by its location on the shelves. This is what the Periodic Table does for chemical elements.

Structurally, the Periodic Table arranges elements in order of increasing atomic number, which is the number of protons in an atom's nucleus. But it's not just a linear array; it's divided into rows called 'periods' and columns known as 'groups' or 'families.' Each period corresponds to the highest energy level that electrons occupy in an atom, while each group contains elements with similar properties and the same number of valence electrons—the electrons present in the outermost shell, which determine an element's chemical behavior.

The beauty of the Periodic Table lies in its predictability. By knowing the period and group of an element, you can predict its valence electron configuration. This is crucial because the number of valence electrons dictates how an element will bond with others, defining the types of compounds it can form. For instance, elements in Group 1 have one valence electron, making them highly reactive and eager to bond with elements that have seven valence electrons, like those in Group 17.

Electron Configuration

Electron configuration might seem like a complex dance of electrons hopping from one energy level to another, but it's a core principle that helps understand an element's chemical behavior. In learning about electron configurations, we typically use the Aufbau principle, which states that electrons fill lower energy levels before moving to higher ones.

The distribution of electrons across the atom's shells defines its electron configuration. Since valence electrons are involved in bonding, knowing how to determine valence electrons from electron configurations is like having a secret code to predicting chemical reactions. Simplistically, an atom's electron configuration follows a 'map' given by orbital filling order, which can be predicted by the Periodic Table. Elements with a similar electron configuration in their valence shell will demonstrate similar chemical properties, hence the grouping of elements on the Periodic Table.

For example, take sulfur—the exercise tells us it has six valence electrons because it sits in Group 16. Its electron configuration ends in 'p⁴,' which indicates that there are four electrons occupying the p orbitals in the third energy level, corresponding to the number of valence electrons that need to be filled to reach the noble gas configuration of the next period.

Chemical Elements

Chemical elements are the individual building blocks of matter, each containing a unique set of properties that differentiate it from other elements. These properties include atomic number, mass number, and, importantly for discussion, valence electrons.

The atomic number, which identifies each element, is the count of protons in an atom's nucleus. But when it comes to the interactions between elements, what's on the outside counts more: the valence electrons. These are the electrons that determine an element’s ability to bond with others, thus forming molecules and compounds. For example, aluminum (Al) is an element with 3 valence electrons, which means it can easily bond with nonmetals that have 5, 6, or 7 valence electrons to form stable compounds.

Understanding the properties of chemical elements is not only crucial for predicting how substances will behave in chemical reactions but also for practical applications. Knowing an element’s characteristics, such as reactivity and preferred bonding partners, can aid us in everything from designing new materials to developing pharmaceuticals. For instance, arsenic (As), despite its notoriety, has applications in semiconductors and light-emitting diodes (LEDs) due to its valence electron configuration.