The key difference between sodium chloride and potassium chloride is that the electronegativity difference between K and Cl is higher than that of Na and Cl.
Sodium chloride and potassium chloride are ionic compounds. Both are solids, and their cations and anions are in a closely packed structure. These are group 1 metals, which have the capability to make +1 cations. Chloride is the -1 anion made by group 7 element, chlorine. Since group 1 elements are electropositive and group seven elements are electronegative; their electronegativity difference is larger. Therefore, they form ionic bonds. Potassium is more electropositive than sodium, so the electronegativity difference between K and Cl is higher than that of Na and Cl.
CONTENTS
1. Overview and Key Difference
2. What is Sodium Chloride
3. What is Potassium Chloride
4. Side by Side Comparison – Sodium Chloride vs Potassium Chloride in Tabular Form
5. Summary
What is Sodium Chloride?
Sodium chloride, or salt, is a white colour crystal with the molecular formula NaCl. It is an ionic compound. Sodium is a group 1 metal and forms a +1 charged cation. Furthermore, its electron configuration is 1s2 2s2 2p6 3s1. It can release one electron, which is in 3s suborbital and produces a +1 cation.
Electronegativity of sodium is very low, allowing it to form cations by donating an electron to a higher electronegative atom (like halogens). Therefore, sodium often makes ionic compounds. Chlorine is a nonmetal and has the ability to form a -1 charged anion. Its electron configuration is 1s2 2s2 2p6 3s2 3p5. Since the p sublevel should have 6 electrons to obtain the Argon noble gas electron configuration, chlorine has the ability to attract an electron. With the electrostatic attraction between the Na+ cation and the Cl– anion, NaCl has obtained a lattice structure.
Figure 01: Table Salt
In the crystal, six chloride ions surround each sodium ion, and each chloride ion is surrounded by six sodium ions. Due to all the attractions between ions, the crystal structure is more stable. The number of ions present in the sodium chloride crystal varies with the size of it. Moreover, this compound is easily soluble in water and makes a salty solution.
Aqueous sodium chloride and molten sodium chloride can conduct electricity due to the presence of ions. The production of NaCl is normally via evaporating sea water. Moreover, we can produce this compound by chemical methods, such as adding HCl into sodium metal. These are useful as food preservatives, in food preparations, as a cleansing agent, for medical purposes, etc.
What is Potassium Chloride?
Potassium chloride, or KCl, is an ionic solid. It is in the form of white colour. It’s melting point is about 770 °C, and the boiling point is 1420 °C. Potassium chloride is mainly useful in making fertilizers since plants need potassium for their growth and development.
Figure 02: Potassium Chloride
KCl, being a salt, is highly soluble in water. Therefore, it readily releases potassium into soil water so that plants can take in potassium easily. This is also useful in medicine and food processing. Further, potassium chloride is important in making potassium hydroxide and potassium metal.
What is the Difference Between Sodium Chloride and Potassium Chloride?
Sodium chloride or salt is a white colour crystal with the molecular formula NaCl. On the other hand, potassium chloride or KCl is an ionic solid. The key difference between sodium chloride and potassium chloride is that the electronegativity difference between K and Cl is higher than that of Na and Cl. Molar mass of KCl is higher than that of NaCl’; the molar mass of sodium chloride is 58.44 g/mol, and for potassium chloride, it is 74.55 g/mol. Apart from that, people who don’t want to intake Na can have KCl salt, instead of NaCl table salt.
Summary – Sodium Chloride vs Potassium Chloride
Potassium chloride is KCl and sodium chloride is NaCl. Potassium is more electropositive than sodium, so the electronegativity difference between K and Cl is higher than that of Na and Cl.
Reference:
1. “Sodium Chloride.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.
Image Courtesy:
1. “Sodium chloride 2” By Chemicalinterest – Own work (Public Domain) via Commons Wikimedia
2. “Potassium chloride (2)” By Chemicalinterest – Own work (Public Domain) via Commons Wikimedia