Question

Which of elements \(1-36\) have one unpaired electron in the ground state?

Short answer

The elements from 1 to 36 with one unpaired electron in the ground state are: Hydrogen, Lithium, Boron, Sodium, Aluminum, Potassium, and Gallium.

Step-by-step solution

Understand electron configuration

Electron configuration is the arrangement of electrons in atomic orbitals in the most stable configuration for an atom. Electrons fill the orbitals in the order of increasing energy levels, following the Aufbau principle. The order in which orbitals are filled is given by: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p and so on. For this exercise, we will only need configurations up to element 36, so we will only consider the orbitals up to 4p.

Identify elements with one unpaired electron

We need to go through the elements 1 to 36 and find the ones with one unpaired electron in the ground state. Unpaired electrons are those that do not have a partner with opposite spin in the same orbital. Here are the electron configurations for the relevant elements: 1. 1s^1 (Hydrogen) 2. 1s^2 (Helium) 3. 1s^2 2s^1 (Lithium) 4. 1s^2 2s^2 (Beryllium) 5. 1s^2 2s^2 2p^1 (Boron) 6. 1s^2 2s^2 2p^2 (Carbon) 7. 1s^2 2s^2 2p^3 (Nitrogen) 8. 1s^2 2s^2 2p^4 (Oxygen) 9. 1s^2 2s^2 2p^5 (Fluorine) 10. 1s^2 2s^2 2p^6 (Neon) 11. 1s^2 2s^2 2p^6 3s^1 (Sodium) 12. 1s^2 2s^2 2p^6 3s^2 (Magnesium) 13. 1s^2 2s^2 2p^6 3s^2 3p^1 (Aluminum) 14. 1s^2 2s^2 2p^6 3s^2 3p^2 (Silicon) 15. 1s^2 2s^2 2p^6 3s^2 3p^3 (Phosphorus) 16. 1s^2 2s^2 2p^6 3s^2 3p^4 (Sulfur) 17. 1s^2 2s^2 2p^6 3s^2 3p^5 (Chlorine) 18. 1s^2 2s^2 2p^6 3s^2 3p^6 (Argon) 19. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 (Potassium) 20. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 (Calcium) 21 to 30. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^1 to 3d^10 (Scandium to Zinc) 31. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^1 (Gallium) 32. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^2 (Germanium) 33. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^3 (Arsenic) 34. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^4 (Selenium) 35. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^5 (Bromine) 36. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 (Krypton) From the above electron configurations, the elements with one unpaired electron in the ground state are: Hydrogen (1s^1), Lithium (2s^1), Boron (2p^1), Sodium (3s^1), Aluminum (3p^1), Potassium (4s^1), and Gallium (4p^1).

List the elements with one unpaired electron

The elements from 1 to 36 with one unpaired electron in the ground state are: 1. Hydrogen 2. Lithium 3. Boron 4. Sodium 5. Aluminum 6. Potassium 7. Gallium

Key concepts

Ground State

Every atom has a unique configuration of electrons that defines its most stable condition. This stable condition is known as the "ground state." In the ground state, electrons occupy the lowest available energy levels around the nucleus.
Being in the lowest energy levels means there is minimal energy potential for the electron, and therefore, the atom is stable.
When we write out electron configurations for an atom, we represent its ground state. For example, hydrogen with a configuration of \(1s^1\) is in its ground state, where its single electron resides in the lowest possible energy orbital, which is the 1s orbital.

Unpaired Electron

An unpaired electron is simply an electron that exists alone in an atomic orbital, without a partner of opposite spin. Electrons tend to form pairs within orbitals, aligning in opposite spins to maintain balance in charge and energy.
However, sometimes, due to the total number of electrons and their distribution among orbitals, there are electrons left unpaired.

• Unpaired electrons result in magnetic properties, as they have a net spin that can interact with external magnetic fields.
• For example, in the electron configuration of boron, \(1s^2 2s^2 2p^1\), there is one unpaired electron in the 2p orbital.

When examining elements to identify those with unpaired electrons, it's crucial to understand how electrons fill orbitals based on their energy levels.

Aufbau Principle

The Aufbau Principle is fundamental in understanding how electrons fill atomic orbitals. According to this principle, electrons occupy the lowest available energy levels before filling higher levels. It’s like claiming seats in a cinema—you start from the front row and move back only when needed.
The term "Aufbau" is German for "building up," reflecting how electrons build up around an atomic nucleus.

• This principle, alongside Hund's rule and the Pauli exclusion principle, helps predict electronic configurations.
• Under the Aufbau principle, hydrogen, with one electron, will fill the \(1s\) orbital first, while calcium, with twenty electrons, will fill up to the \(4s\) orbital, as described in its electron configuration: \(1s^2 \;2s^2 \;2p^6 \;3s^2 \;3p^6 \;4s^2\).

Atomic Orbitals

Atomic orbitals are regions around an atom's nucleus where electrons are likely to be found. They are defined by specific shapes and energy levels. Each orbital can hold a maximum of two electrons with opposite spins.
Orbitals are designated by letters \(s\), \(p\), \(d\), and \(f\), with \(s\) orbitals being spherical and \(p\) orbitals being dumbbell-shaped.

• For instance, the \(1s\) orbital indicates the first energy level with a spherical shape.
• The \(3p\) orbitals are at the third energy level, and each \(p\) orbital has three different orientations: \(p_x\), \(p_y\), and \(p_z\).
• Electrons first fill lower energy orbitals (like \(1s\), then \(2s\), etc.) as per the Aufbau principle.

Understanding atomic orbitals is key to mastering electron configuration and the arrangement of elements on the periodic table.