Question

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

Short answer

The elements are: (a) Chlorine (Cl), (b) Gallium (Ga), (c) Iron (Fe), and (d) Rubidium (Rb).

Step-by-step solution

Identify Element for (a)

The electron configuration \( [\mathrm{Ne}] 3s^{2} 3p^{5} \) suggests that the element has the same electron configuration as Neon (Ne) for the first 10 electrons, plus 2 electrons in the 3s subshell, and 5 electrons in the 3p subshell. The total number of electrons is 17, which corresponds to the element Chlorine (Cl).

Identify Element for (b)

The electron configuration \( [\mathrm{Ar}] 4s^{2} 3d^{10} 4p^{1} \) indicates that the element builds upon Argon (Ar), followed by filling the 4s subshell with 2 electrons, completely filling the 3d subshell with 10 electrons, and adding 1 electron to the 4p subshell. The total is 18 (Ar) + 13 (additional electrons) for a total of 31, identifying the element as Gallium (Ga).

Identify Element for (c)

By the electron configuration \( [\mathrm{Ar}] 4s^{2} 3d^{6} \) the element is based on Argon (Ar). It has an additional 2 electrons in the 4s subshell and 6 in the 3d subshell. Adding these to Argon's 18 electrons gives us 26 electrons in total, which is the element Iron (Fe).

Identify Element for (d)

The electron configuration \( [\mathrm{Kr}] 5s^{1} \) starts with Krypton (Kr). Since it is followed by a single electron in the 5s subshell, the element must have 36 (Kr) + 1 additional electron, for a total of 37 electrons, which identifies the element as Rubidium (Rb).

Key concepts

Understanding the Periodic Table

The periodic table is a comprehensive chart that organizes all known chemical elements in a systematic way based on their atomic number, which is the number of protons in the nucleus of an atom. Elements are arranged in rows called periods and columns known as groups or families, with each group sharing similar chemical properties.

For students working on electron configurations, the periodic table is an invaluable tool. As you move from left to right across a period, each element has one more proton and is typically one electron more than the previous element. Elements are also grouped by their electron configurations; for instance, the noble gases found in the rightmost column have full electron outer shells, making them largely non-reactive.

Element Identification Using Electron Configurations

When identifying an element from its electron configuration, you can use the periodic table to help you understand how the subshells are filled. For instance, the first two electrons in a neutral atom will fill the 1s orbital. The next two go into the 2s orbital, followed by six into the 2p orbitals, and so on. Recognizing these patterns is key in deciphering the element being described.

Atomic Structure Fundamentals

Atomic structure refers to the composition and arrangement of protons, neutrons, and electrons within an atom. The protons and neutrons reside in the nucleus at the center of the atom, while electrons orbit the nucleus in various energy levels or shells. These energy levels contain subshells (s, p, d, and f) where electrons are found.

Understanding atomic structure is essential for mastering electron configurations. Electrons fill subshells in a particular order based on their energy levels, often described by Aufbau's principle, which states that electrons fill lower energy orbitals first. Additionally, Hund's rule explains that electrons will fill an unoccupied orbital before they pair up.

Electron Configuration Patterns

Electron configurations follow a 'map' of where the electrons are located around the nucleus. For example, the notation \(2s^{2}\) implies there are two electrons in the 's' orbital of the second energy level. By understanding these notations and rules, the atomic structure of an element becomes clear, facilitating the identification process as described in the solved exercise.

Chemical Elements and Their Properties

Chemical elements are substances consisting of only one type of atom, distinguished by the number of protons in the nucleus, which is the atomic number. Each element has unique properties and a specific electron configuration that can predict chemical reactions and bonding behavior.

The properties of elements are influenced by their atomic structure, particularly the configuration of their valence electrons, or the electrons in the outermost shell. For example, elements with a full valence shell are generally inert, whereas elements with only one valence electron, like the alkali metals, are highly reactive.

Real-World Application

Understanding an element's electron configuration has practical applications. In the exercise, recognizing the electron configurations and using the corresponding periodic number helps identify the element. This knowledge is crucial for predicting how an element will interact with others, its role in chemical reactions, or its utility in various technological or industrial applications.