Question

Look for antimony in the periodic table. (a) Write the complete electron configuration for an atom of antimony. (b) Write the shorthand electron configuration for an atom of antimony. (c) How many valence electrons does antimony have? (d) Underline the valence electrons in the shorthand electron configuration.

Short answer

Complete configuration: 1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6 4d^{10} 5s^2 5p^3; Shorthand configuration: [Kr] 5s^2 4d^{10} 5p^3; Valence electrons: 5; Underlined valence electrons in shorthand: [Kr] 5s^2 4d^{10} 5p^3.

Step-by-step solution

Find Antimony in the Periodic Table

Locate the element antimony in the periodic table using its symbol Sb. Note its atomic number, which is 51. This indicates that a neutral antimony atom contains 51 protons and, consequently, 51 electrons.

Write the Complete Electron Configuration

Write out the electron configuration for antimony by filling the electrons into the atomic orbitals according to the Aufbau principle, Hund's rule, and the Pauli exclusion principle. The order of the orbitals begins with 1s, followed by 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, and so on. Continue until you have accounted for all 51 electrons.

Write the Shorthand Electron Configuration

Identify the last noble gas that precedes antimony in the periodic table, which is krypton (Kr), with an atomic number of 36. Write the shorthand electron configuration by starting with the symbol for krypton in brackets, followed by the remaining orbitals that are filled after krypton.

Determine the Number of Valence Electrons

Look at the group number for antimony in the periodic table. Antimony is in group 15, which means it will have 5 valence electrons. Alternatively, you can count the electrons in the outermost (highest energy level) s and p subshells from the electron configurations you've written.

Underline the Valence Electrons in Shorthand Notation

In the shorthand electron configuration, underline the electrons that belong to the highest energy level, which constitutes the valence electrons. For antimony, underline the electrons that come after the noble gas krypton in the configuration.

Key concepts

Understanding the Periodic Table

The periodic table is a cornerstone of chemistry and physics, providing a systematic arrangement of the known chemical elements. When you look at the periodic table, you see an organized chart where elements are positioned based on their atomic numbers, electron configurations, and recurring chemical properties. Essential to the periodic table is the concept of periods (horizontal rows) and groups (vertical columns).

Antimony, with the chemical symbol Sb, is found towards the right side of the table in group 15. This placement gives significant insight into its chemical behavior. For example, the group number can help you determine the number of valence electrons for many elements, including antimony. In the study of chemistry, becoming comfortable with the periodic table is a key step towards understanding the electron configuration and reactivity of elements like antimony.

The Role of Valence Electrons

Valence electrons are the electrons that reside in the outermost shell of an atom, and they play a pivotal role in chemical reactions. These electrons determine how an element will interact with others, including the types of bonds it will form. Antimony, which appears in group 15 of the periodic table, has five valence electrons. This means that when writing the electron configuration for antimony or predicting its chemical behavior, it is critical to recognize that these valence electrons are the most reactive. It's worth highlighting that the valence electrons are the ones typically involved in forming bonds, and, therefore, dictate much of an element's chemistry.

Applying the Aufbau Principle

One of the guiding principles used in writing electron configurations is the Aufbau principle. This principle states that electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. When determining the electron configuration for antimony, electrons are placed starting from the lowest energy orbital, which is the 1s orbital, and continue to fill up in order of increasing energy until all 51 electrons are accounted for. This concept helps students understand the structure of the electron cloud and is invaluable when trying to grasp why elements exhibit their particular chemical behaviors.

Understanding Hund's Rule

Hund's rule is key to figuring out the arrangement of electrons in orbitals with the same energy, also known as degenerate orbitals. According to Hund's rule, electrons will fill empty orbitals singly before pairing up. They will also have parallel spins until all orbitals at a given energy level have one electron. When you look at the electron configuration of antimony, Hund's rule explains the distribution of electrons in its p orbitals, ensuring that each orbital gets one electron before any pairing occurs. This principle is essential for the proper representation of electron configurations and helps us understand magnetic properties of an element as well.

Implementing the Pauli Exclusion Principle

The Pauli exclusion principle states that no two electrons in an atom can have the same four quantum numbers. In simpler terms, an orbital can hold at most two electrons, and these electrons must have opposite spins. When filling in the electron configuration for antimony or any other element, keeping the Pauli exclusion principle in mind ensures that electrons are correctly paired within orbitals. Adhering to this rule is fundamental when predicting the electron configurations, as errors can lead to misunderstanding an element's chemical and physical properties.