Question

Find the electron configuration of an isolated indium atom in the lowest energy state. How many electrons are found around the atom? Repeat for a Cl -ion.

Short answer

Indium: 49 electrons, Cl⁻: 18 electrons.

Step-by-step solution

Determine the Atomic Number

Indium has an atomic number of 49, which means it has 49 electrons when neutral.

Apply the Electron Configuration Order

Fill the electron orbitals in the order of increasing energy using the Aufbau principle. The order is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p.

Assign Electrons to Subshells

Starting from 1s, fill each subshell to its maximum capacity: 1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5p¹. Thus, the electron configuration for indium is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p¹.

Determine Electrons Around the Atom

For a neutral indium atom, there are 49 electrons as its electron configuration completely fills the given subshells.

Electron Configuration of Cl⁻ Ion

The chlorine atom has an atomic number of 17, which means it normally has 17 electrons. As a Cl⁻ ion, it gains one more electron, making it 18 electrons. Fill the electron orbitals for Cl⁻ to get the configuration: 1s² 2s² 2p⁶ 3s² 3p⁶. This is the configuration for argon, indicating Cl⁻'s extra electron fills the 3p subshell.

Determine Electrons in Cl⁻ Ion

Cl⁻ ion, with an electron configuration of 1s² 2s² 2p⁶ 3s² 3p⁶, contains 18 electrons.

Key concepts

Atomic Number

The atomic number of an element is a fundamental concept in chemistry. It tells us the number of protons present in the nucleus of an atom. Since atoms are electrically neutral, the atomic number also equals the number of electrons surrounding the nucleus.
The atomic number is crucial because it defines the chemical identity of an element. For example, indium has an atomic number of 49, meaning it has 49 protons and, when neutral, 49 electrons.

• The atomic number can be found on the periodic table, where elements are arranged in order of increasing atomic number.
• It's denoted by the symbol 'Z'.

Understanding the atomic number helps in determining electron configurations and chemical reactivity.

Aufbau Principle

The Aufbau Principle is a fundamental rule used to determine the electron configuration of an atom. It states that electrons occupy the lowest energy orbitals first before filling higher energy ones. This approach helps in predicting how electrons are distributed in an atom's orbitals.
According to this principle, orbitals are filled in the order of increasing energy levels. This generally follows the sequence: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, and so on.

• Each type of subshell has a specific capacity: s can hold 2 electrons, p can hold 6, d can hold 10, and f can hold 14.
• By following the Aufbau Principle, we ensure that the electron configuration is in its ground state, or most stable configuration.

Applying this principle is fundamental in constructing the electron configurations of atoms, such as determining the arrangement of electrons in indium and chloride ions.

Indium Atom

Indium is a metallic element with interesting properties, most notably its softness and malleability. In its atomic form, indium has an atomic number of 49. This indicates that a neutral indium atom has 49 electrons.
To discover indium's electron configuration, electrons are added to orbitals using the Aufbau Principle:

• 1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5p¹.

This configuration shows how indium's electrons are distributed across various energy levels. Understanding its electron configuration is important for predicting indium's chemical behavior and bonding abilities.

Chloride Ion

A chloride ion (Cl⁻) represents a chlorine atom that has gained an extra electron to achieve a more stable electron configuration. Chlorine itself has an atomic number of 17, meaning it normally has 17 electrons.
When chlorine gains an electron, it becomes Cl⁻ and has 18 electrons. This is isoelectronic with argon, a noble gas, explaining its stable electron configuration:

• 1s², 2s², 2p⁶, 3s², 3p⁶.

This filled outer shell makes the chloride ion less reactive than a neutral chlorine atom. Understanding this transformation into a chloride ion is essential for grasping concepts in ionic bonding and salt formation.