Problem 9 - Chemistry and Chemical Reactivity

Question

When a potassium atom becomes a monatomic ion, how many electrons does it lose or gain? What noble gas atom has the same number of electrons as a potassium ion?

Step-by-Step Solution

Answer

Potassium loses 1 electron to form \( \text{K}^+ \) and has the same number of electrons as argon.

Step 1: Understanding Potassium Atom

A neutral potassium atom has an atomic number of 19, which means it has 19 protons and 19 electrons.

Step 2: Identifying the Ion Formation

Potassium tends to lose electrons to achieve a stable electron configuration. Specifically, it loses one electron to form a positive ion with a charge of +1, written as \( \text{K}^+ \).

Step 3: Determining Electron Count in Ion

After losing one electron, the potassium ion has a total of 18 electrons.

Step 4: Finding the Noble Gas with the Same Electron Count

The noble gas with 18 electrons is argon (Ar). Thus, a potassium ion has the same number of electrons as an argon atom.

Key Concepts

Potassium Ions

Potassium ions play a crucial role in both chemistry and biology. Let's delve into how these ions form and their significance.
A neutral potassium atom has 19 electrons, matching its atomic number, which is 19. To become stable, potassium tends to lose one electron.
As a result, it transforms into a positively charged ion, known as a potassium ion, denoted as \( \text{K}^+ \). This ion now has 18 electrons, having shed one to achieve stability.
Potassium ions are vital in various biological functions, such as maintaining proper nerve and muscle function.

Electron Configuration

The electron configuration describes how electrons are distributed in an atom or ion. It follows a specific rule known as the Aufbau principle, filling orbitals in order of increasing energy.
Potassium's neutral atom has the electron configuration of \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 \).
When potassium loses one electron to form a \( \text{K}^+ \) ion, it attains an electron configuration of \( 1s^2 2s^2 2p^6 3s^2 3p^6 \).

• This loss of the outermost electron leads to a more stable configuration.
• This matches the electron arrangement of a noble gas, which is more stable energetically.

Understanding electron configuration helps in explaining chemical reactivity and bonding.

Noble Gases

Noble gases are found in Group 18 of the periodic table and are known for their chemical inertness.
They have full electron shells, which makes them highly stable and unreactive. Examples include helium, neon, and argon.
Potassium ions, after shedding one electron, have an electron count similar to argon, a noble gas.

• This is why achieving a noble gas electron configuration is often a driving force for ion formation.
• The stability of noble gases is due to their complete electron orbitals, making them unlikely to participate in chemical reactions.

By observing noble gases, scientists understand the stable electron configurations atoms strive towards.

Atomic Structure

Atomic structure refers to the arrangement of protons, neutrons, and electrons within an atom.
Key components include:

• Protons: Positively charged particles found in the nucleus.
• Neutrons: Neutral particles also located in the nucleus.
• Electrons: Negatively charged particles orbiting the nucleus in various energy levels.

Each element's atomic structure determines its properties and behavior. For potassium, its 19 protons and 19 electrons give it a unique identity and chemical characteristics.
When potassium forms a \( \text{K}^+ \) ion, its atomic structure changes as it loses an electron, impacting its chemical interactions and stability.