Question

Using a four-block periodic table as a guide, determine the ground-state electron configuration of copper (Cu). Answer: You should have arrived at \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2} 3 d^{9}\), because copper is nine deep into the d block of period 4 . However, copper is one of those exceptions, and its true electron configuration is \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{1} 3 d^{10}\).

Short answer

The ground-state electron configuration of copper (Cu) is: \(1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{1} 3d^{10}\), due to copper being an exception and having a filled d orbital for higher stability.

Step-by-step solution

Identify the element in the periodic table

Locate copper (Cu) in the periodic table. Copper has an atomic number of 29, meaning it has 29 electrons in its neutral state. It is found in period 4 and the d block.

Determine the electron filling order

The electron filling order is based on the Aufbau principle and is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p. This order is based on the principle that electrons fill the lowest-energy orbitals first.

Fill the electrons in the electron filling order

We will fill in the electrons for copper sequentially until all 29 electrons are placed in the corresponding orbitals. Follow the electron filling order and the maximum capacity for each orbital (s holds 2, p holds 6, d holds 10, and f holds 14). 1. Fill 1s: \(1s^{2}\) (2 electrons) 2. Fill 2s: \(2s^{2}\) (2 electrons) 3. Fill 2p: \(2p^{6}\) (6 electrons) 4. Fill 3s: \(3s^{2}\) (2 electrons) 5. Fill 3p: \(3p^{6}\) (6 electrons) 6. Fill 4s: \(4s^{2}\) (2 electrons) 7. Fill 3d: \(3d^{9}\) (9 electrons)

Consider exceptions (Copper)

The electron configuration obtained so far is: \(1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{2} 3d^{9}\). However, copper is an exception, and its electron configuration is actually \(1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{1} 3d^{10}\). This occurs because a filled or half-filled d orbital has higher stability. In this case, one electron from the 4s orbital moves to the 3d orbital to attain a full d orbital.

Final Answer

The correct ground-state electron configuration for copper (Cu) is: \(1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{1} 3d^{10}\).

Key concepts

Periodic Table

The periodic table is like a map for chemists and anyone interested in the substances that make up our world. It organizes all known elements by increasing atomic number, which is the number of protons in an atom's nucleus. Each row of the table is called a period, indicating that elements have increasing energy levels of electrons.

The elements are also grouped into columns known as groups or families, which have similar chemical properties. The periodic table divides elements into blocks (s, p, d, and f) based on the subshell that is being filled with electrons in their ground-state electron configurations. This systematic layout helps us predict various properties of elements, including their reactivity and how they might interact with others.

Aufbau Principle

Understanding how electrons are arranged in an atom is crucial in chemistry, and the Aufbau principle guides us in this. This fundamental rule states that electrons fill the lowest energy orbitals first before moving to higher energy levels.

The word 'Aufbau' is German for 'building up', perfectly describing the electron filling process. Electrons are added one at a time to the lowest energy orbitals until all of them are placed within the atom. This principle helps in predicting the likely electronic configuration of an element, which plays a key role in its chemical behavior.

Ground-State

An atom's ground state refers to its lowest energy state, where all electrons are in the lowest possible energy levels according to the Aufbau principle. In this baseline state, the atom is stable, and its electrons are arranged in a specific pattern around the nucleus, representing the most likely locations for the electrons as determined by quantum mechanics.

An understanding of the ground-state electron configuration is fundamental for explaining an element's chemical bonds, reactivity, and physical properties. It's what we use as a starting point when looking at how atoms combine to form molecules or how they behave in different chemical reactions.

Atomic Number

The atomic number is one of the most basic and important characteristics of an element. It is equal to the number of protons in the nucleus of an atom and it uniquely identifies a chemical element. Since neutral atoms have equal numbers of protons and electrons, the atomic number also tells us the number of electrons in a neutral atom.

The periodic table is arranged in order of increasing atomic number. Understanding the atomic number allows us to determine the position of an element in the periodic table and thus predict a lot about the element's properties, including its electron configuration. This number is so fundamental that elements are defined by their atomic number rather than the number of other subatomic particles they possess.