Question

Use the periodic table to identify the element with each electron configuration. (a) \([\mathrm{Ne}] 3 s^{1}\) (b) \([\mathrm{Kr}] 5 s^{2} 4 d^{10}\) (c) \([X e] 6 s^{2}\) (d) \([\mathrm{Kr}] 5 s^{2} 4 d^{10} 5 p^{3}\)

Short answer

The elements with the given electron configurations are: (a) Sodium (Na), (b) Cadmium (Cd), (c) Barium (Ba), and (d) Antimony (Sb).

Step-by-step solution

Identifying Element for Configuration (a)

The given electron configuration, \(\mathrm{[Ne]} 3s^1\), indicates that the element has the same electron configuration as Neon (Ne) with an additional electron in the 3s orbital. Since Neon has 10 electrons, the additional electron gives us a total of 11 electrons which is the electron configuration of Sodium (Na).

Identifying Element for Configuration (b)

The configuration \(\mathrm{[Kr]} 5s^2 4d^{10}\) starts with Krypton (Kr) as the core. Krypton has 36 electrons. The added electrons \(5s^2 4d^{10}\) account for an additional 12 electrons, making a total of 48 electrons. This is the electron configuration of Cadmium (Cd).

Identifying Element for Configuration (c)

The configuration \(\mathrm{[Xe]} 6s^2\) has Xenon (Xe) as the core. Xenon contains 54 electrons. Adding the two 6s electrons, the total comes to 56 electrons, which is the electron configuration of Barium (Ba).

Identifying Element for Configuration (d)

For the configuration \(\mathrm{[Kr]} 5s^2 4d^{10} 5p^3\), the electron configuration builds upon Krypton (Kr), which has 36 electrons. Adding 5s, 4d, and 5p electrons, the total number of electrons becomes 51 (36 + 2 + 10 + 3). This corresponds to Antimony (Sb).

Key concepts

The Periodic Table

Understanding the periodic table is essential for identifying elements based on electron configurations. It's an organized chart that displays all known chemical elements arranged by increasing atomic number. What's interesting is that the table is also divided into periods (horizontal rows) and groups (vertical columns), which reflect the elements' recurring properties.

Electron configurations provide clues about an element's location on the periodic table. For instance, elements in the same group typically have similar valence electron configurations, explaining their resemblance in chemical behavior. When students recognize the structure of the periodic table with respect to electron configurations, they can more efficiently deduce the identity of an element, as shown in the exercise.

Atomic Structure

The atomic structure concept clarifies how electrons are arranged in atoms. An atom consists of a nucleus, containing protons and neutrons, and electrons that orbit around the nucleus in different energy levels or shells. The primary principle here is that electrons fill lower energy orbitals first before moving to higher ones.

Electron configurations represent the arrangement of electrons in orbitals, and by understanding this order—1s, 2s, 2p, 3s, and so on—you can determine which electron shell is being filled. The exercise above exploited this understanding to pinpoint which period and group the elements belonged to on the periodic table.

Chemical Elements

Chemical elements are pure substances consisting of only one type of atom, characterized by a specific number of protons in their nuclei. The difference in proton number, known as the atomic number, distinguishes one element from another. Elements can be metals, nonmetals, or metalloids, and they come with unique electron configurations that dictate their chemical properties.

Using electron configurations, such as those provided in the exercise, can help you identify chemical elements. This is crucial as knowing an element's identity allows us to understand its characteristics and how it reacts with other elements.

Electron Orbital

Electron orbitals are regions within an atom where electrons are likely to be found. They come in various shapes (spherical for s orbitals, dumbbell-shaped for p orbitals, etc.) and are key to understanding electron configurations. Each type of orbital can hold a set number of electrons: s orbitals hold up to 2, p orbitals up to 6, d orbitals up to 10, and f orbitals up to 14.

The exercise illustrates how electron orbitals determine an element’s electron configuration. Recognizing the sequence and the capacity of these orbitals provides a foundation for predicting and understanding the properties of different elements.