Question

Write the abbreviated electron configurations for (a) Al, (b) Se, (c) \(\mathrm{Ba}\) (d) \(\mathrm{Sb},\) and \((\mathrm{e}) \mathrm{Gd}\)

Short answer

[Ne] 3s^2 3p^1 for Al, [Ar] 4s^2 3d^{10} 4p^4 for Se, [Xe] 6s^2 for Ba, [Kr] 5s^2 4d^{10} 5p^3 for Sb, and [Xe] 4f^7 5d^1 6s^2 for Gd.

Step-by-step solution

Identify the Nearest Noble Gas

Determine the noble gas that comes before the element in the periodic table, which will be used to abbreviate the electron configuration.

Write Electron Configurations

Write down the full electron configurations for each element up to that noble gas, followed by the configuration for the remaining electrons.

Abbreviate Electron Configurations

Replace the noble gas core electron configuration with the noble gas's symbol in brackets to represent that part of the configuration.

Key concepts

Understanding the Periodic Table

The periodic table is a masterpiece of organized chemical information and the blueprint for the makeup of everything around us. It is vital in the world of chemistry as it organizes elements in a structured manner, allowing us to see at a glance how elements relate to one another.

At the fundamental level, the table is arranged in order of increasing atomic number, which is the number of protons in an element's nucleus. Elements are placed in specific groups and periods. Groups are the vertical columns, which usually have elements with similar chemical behaviors. Periods are the horizontal rows, indicating increasing energy levels.

Key takeaway for understanding electron configurations is that elements in the same group typically have a similar configuration pattern, especially in regards to their valence electrons -- the ones involved in chemical reactions and bonding.

Noble Gas Configuration

Diving into the noble gas configuration, these elements are a cornerstone of simplifying electron notations. Found in Group 18 of the periodic table, noble gases have complete valence electron shells, which makes them chemically stable and largely nonreactive. This natural stability is why they are used as a shorthand in electron configurations.

As you write the electron configuration for an atom, you can abbreviate the part of the configuration that mirrors a noble gas to save time and space. For example, neon (Ne) has a configuration of 1s²2s²2p⁶, which is the ending configuration for all elements preceding it, up to sodium (Na), which starts its unique configuration from 3s¹. By recognizing these patterns, you can effectively document and understand electron distribution which is crucial for predicting how an atom will behave.

Mastering Electron Configuration Notation

To bring everything together, electron configuration notation is essential for denoting where electrons are within an atom. This level of detail is critical in predicting the chemical, electrical, and physical properties of matter.

Electron configurations are written using numbers to represent energy levels, letters to denote sublevels -- such as s, p, d, and f -- and superscripts to indicate the number of electrons in each sublevel. The goal is to fill the sublevels according to their energy, following rules like the Aufbau Principle, which suggests that electrons fill lower energy levels before moving to higher ones.

For example, the full electron configuration for aluminum (Al), which is in period 3, group 13, is 1s²2s²2p⁶3s²3p¹. Notice how it fills the 3p sublevel after the 3s is complete. With abbreviation using noble gases, the configuration is written as [Ne]3s²3p¹, where [Ne] represents the configuration of neon, immediately preceding aluminum on the periodic table.