Question

Write the complete electron configuration for each of the following elements: (a) scandium (b) rubidium (c) bromine (d) sulfur

Short answer

The complete electron configurations are: (a) Scandium (Sc): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹, (b) Rubidium (Rb): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹, (c) Bromine (Br): 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵, (d) Sulfur (S): 1s² 2s² 2p⁶ 3s² 3p⁴.

Step-by-step solution

Scandium Electron Configuration

Find Scandium (Sc) on the periodic table and note its atomic number (21). Starting with hydrogen, fill the electron orbitals in the order of 1s, 2s, 2p, 3s, 3p, 4s, and then 3d. Remember that the s orbital can hold up to 2 electrons, p orbital can hold up to 6, and d can hold up to 10. The electron configuration of Scandium is then written as: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹.

Rubidium Electron Configuration

Locate Rubidium (Rb) on the periodic table with an atomic number of 37. Following the order of orbitals (1s through 5s), write down the electron configuration as electrons are filled into available orbitals according to the Aufbau principle. The electron configuration for Rubidium is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹.

Bromine Electron Configuration

Identify Bromine (Br) on the periodic table, which has an atomic number of 35. Apply the Aufbau principle to determine the order in which the electrons fill into the orbitals from 1s through 4p. The electron configuration of Bromine is: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵.

Sulfur Electron Configuration

Find Sulfur (S) on the periodic table that has an atomic number of 16. Fill the electrons into the orbitals from 1s up to 3p following the Aufbau principle. The electron configuration for Sulfur is 1s² 2s² 2p⁶ 3s² 3p⁴.

Key concepts

Aufbau Principle

The Aufbau principle is a fundamental concept that dictates how electrons are arranged in an atom's orbitals. The word 'Aufbau' is German for 'building up,' and the principle describes the sequential order in which electrons fill the subatomic orbitals. According to this rule, electrons occupy the lowest energy orbitals first before moving to higher ones. For example, in the case of scandium (Sc), with an atomic number of 21, the electrons fill the 1s orbital, then 2s, and so on, culminating in the 3d orbital, which is higher in energy than 4s but is filled after due to its unique energy levels.

Improving comprehension involves recognizing that the distribution of electrons isn't simply about filling orbitals randomly but adheres to this logical and energetic sequence. Each type of orbital (s, p, d, f) has a different shape and capacity for electrons, playing a crucial role in determining an element's chemical properties. This principle is instrumental not only in electron arrangement but also sets the stage for understanding the chemical behavior of elements.

Orbital Filling Order

The orbital filling order is intimately connected with the Aufbau principle and provides a more detailed map for electron distribution in an atom. Electrons fill the atomic orbitals of the lowest available energy levels before occupying higher levels, following a specific sequence: 1s, 2s, 2p, 3s, 3p, and so forth. Each type of orbital has a defined maximum number of electrons: s can hold 2, p can hold 6, d can hold 10, and f can hold 14.

To practically apply this when deducing configurations like those of rubidium (Rb) or sulfur (S), one should remember the order represents not just energy levels but also the shape and capacity of the orbitals. Identifying this order could be simplified using tricks like the diagonal rule or memorizing the sequence. Understanding the filling order can explain why certain elements exhibit similar chemical properties and is key to predicting the behavior of atoms during chemical reactions.

Periodic Table

The periodic table is not just a chart of elements but a robust framework that encapsulates various atomic properties, including the electron configuration of elements. It reflects the repeating pattern of chemical properties and showcases trends such as electronegativity, atomic radius, and ionization energy. The table is arranged by increasing atomic number and organized into groups and periods. Groups are the columns and represent elements with similar valence electron configurations, leading to comparable chemical properties. Periods are the rows and indicate the energy levels being filled with electrons.

Using bromine (Br) as an example, located in Group 17 and Period 4, one can deduce its electron configuration based on its position. Students will find that the periodic table is an invaluable tool for understanding why elements react in certain ways and how their electrons are structured. By viewing the table as a map of the 'building blocks' of matter, learners can enhance their grasp of both individual elements and the broader patterns in chemistry.