Chlorine and chloride: these two terms sound very similar, and people sometimes use them interchangeably. But they aren’t the same thing!
Chlorine and chloride are chemically related, but they have different properties and play different roles in the world around us.
This article will explain the difference between chlorine (Cl) and chloride (Cl⁻) by breaking down the structure of each and exploring their different properties.
Understanding the difference between these two substances is important in many fields, including chemistry, biology, and environmental science.
Atomic Structure: The Key to Differentiation
The distinction between chlorine and chloride comes down to the arrangement of subatomic particles. Here’s a quick look at each:
Chlorine (Cl): The Neutral Atom
Chlorine is an element, number 17 on the periodic table. As a neutral atom, chlorine has 17 positively charged protons in its nucleus and 17 negatively charged electrons orbiting the nucleus. Because the positive and negative charges are equal, the atom is neutral.
Chloride (Cl⁻): The Anion
Chloride is what’s known as an anion. An anion is an ion with a negative charge. A chloride ion still has 17 protons, but it has picked up an extra electron, giving it 18 electrons in total. That extra electron gives the chloride ion its negative charge.
How chloride ions form
A chloride ion forms when a chlorine atom gains an electron. This usually happens when electrons transfer during a chemical reaction.
Chlorine is very greedy for electrons. Chemists say that it has a high “electron affinity,” meaning that chlorine readily accepts an electron to reach a stable electron configuration. Chlorine also has high “electronegativity,” which means it attracts electrons in chemical bonds.
We can show this in a simple equation:
Cl + e⁻ → Cl⁻
Examples and Reactions
Let’s look at what happens when chlorine and sodium react. Sodium donates an electron to chlorine. This creates a sodium ion (Na+) and a chloride ion (Cl-). Because opposites attract, these ions bond together, creating sodium chloride (NaCl) — good old table salt!
Potassium chloride (KCl) forms in much the same way.
Chloride ions play a vital role in keeping our bodies working correctly. They’re electrolytes that help balance fluids and transmit nerve impulses.
Frequently Asked Questions
Is chloride or chlorine in drinking water?
Drinking water contains both chloride and chlorine, but in different forms and for different reasons. Chlorine is added as a disinfectant to kill harmful bacteria and viruses, ensuring the water is safe to drink. The chlorine used is elemental chlorine (Cl2) or compounds that release chlorine. Chloride, on the other hand, is a naturally occurring ion (Cl–) found in water sources. It’s not added intentionally for disinfection but is a common mineral found in many water supplies.
Is a pool chlorine or chloride?
Pools primarily use chlorine for sanitation, but the chlorine eventually breaks down and forms chloride. When you add chlorine to a pool, it creates hypochlorous acid (HOCl) and hypochlorite ions (OCl–), which are the active sanitizers. As these compounds react with contaminants, they are converted into chloride. So, both chlorine (in its active disinfecting forms) and chloride are present in pool water. Over time, the chloride level increases as more chlorine is used and broken down.
Why does chlorine turn into chloride?
Chlorine converts to chloride through a chemical reaction called oxidation. When chlorine is introduced to water, it creates hypochlorous acid and hypochlorite ions, which are highly reactive and kill bacteria and other organic matter. During this process, the chlorine atoms gain electrons from the substances they are oxidizing. This gain of electrons transforms the chlorine atoms into chloride ions. Essentially, the chlorine does its job by oxidizing contaminants, and in doing so, becomes chloride.
In Summary
The key difference between chlorine and chloride is that chlorine is a neutral atom, while chloride is a negatively charged ion – it’s chlorine’s anion. Understanding this distinction is vital in many scientific fields.
Chloride ions are abundant in nature, especially in saltwater environments, and play a critical role in industrial processes. So, while they’re related, chlorine and chloride aren’t interchangeable.