Difference Between Sodium and Potassium

Main Difference – Sodium vs Potassium

Sodium and potassium are highly reactive chemical elements that can be found in group 1 of the periodic table. They are s block elements because they have their valence electron in the outermost s orbital. Both sodium and potassium are very useful chemical elements because they form a wide variety of chemical compounds. However, there are differences between sodium and potassium since they are two different chemical elements. The main difference between sodium and potassium is that sodium atoms are smaller than potassium atoms.

Key Areas Covered

1. What is Sodium
      – Definition, Chemical Properties, Compounds
2. What is Potassium
      – Definition, Chemical Properties, Isotopes
3. What are the Similarities Between Sodium and Potassium
      – Outline of Common Features
4. What is the Difference Between Sodium and Potassium
      – Comparison of Key Differences

Key Terms: Atomic Number, Atomic Size, Boiling Point, Melting Point, Metal, Photosynthesis, Potassium, Sodium

What is Sodium

Sodium is a chemical element having the atomic number 11 and chemical symbol “Na”. The atomic weight of sodium is about 22.98 amu. Sodium is a metal. Its melting point is 97.79 °C and boiling point is 882.8 °C. At room temperature and pressure, sodium is in the solid phase. Although it has a metallic shiny appearance, it is a soft metal which can be easily cut using a knife. Sodium is in the group 1 of the periodic table. Therefore, it is an s block element. The group 1 elements are known as alkali metals as they can form basic (alkaline) compounds.

Figure 1: Chunks of Sodium in a Vial

Sodium is highly reactive. It readily reacts with oxygen and water. Hence, the metallic form of sodium has fewer applications. It cannot be used as a construction material because it is too soft and highly reactive. When burnt, sodium gives a yellow-orange flame. When a tiny piece of sodium is added to water, it shows a highly explosive reaction.

Sodium forms a number of compounds that are very useful in laboratories as well as in industries. The salts of sodium are alkaline. Some important examples include table salt (NaCl), soda ash (Na₂CO₃), caustic soda (NaOH), and borax (Na₂B₄O₇·10H₂O).

What is Potassium

Potassium is a chemical element having the atomic number 19 and chemical symbol “K”. Potassium is an alkali metal found among the elements of group I in the periodic table. The electron configuration of potassium is [Ar] 4s¹. At room temperature, potassium is in the solid phase. The melting point of potassium is 63.5 °C and the boiling point is 759 °C.

Potassium is an element that is absolutely necessary for both plants and animals. Sir Humphry Davy isolated potassium element by electrolysis of molten potassium hydroxide (KOH). Potassium metal is soft and silvery white in color. It has a very low melting point. Since it is a metal, it is a good electrical conductor. Potassium is the seventh most abundant element on earth. Most commercially available compounds are obtained from electrolysis of certain compounds such as carnallite since elemental potassium is present in water-insoluble sediments and rocks, which makes it is difficult to be extracted.

Figure 2: Potassium Metal

Potassium makes monovalent ion K⁺¹ by removing the electron located in its outermost shell. Hence, it is more likely to have ionic bonds with non-metals or anionic compounds through electrostatic attractions. Potassium can be found in seawater or other salty water sources as the solubilized K⁺¹ ion.

All plants and animals need Potassium as K⁺¹. Plants mainly need it for photosynthesis; it also the primary inorganic cation in the living cell. However, excessive amounts of potassium can be toxic.

Potassium naturally exists as three isotopes. The most abundant isotope is potassium-39, which has equal amounts of protons and neutrons in its atom. The other two isotopes are potassium-41 and potassium-40, which are radioactive.

Similarities Between Sodium and Potassium

Sodium and Potassium are group 1 elements.
Both are alkali metals.
Both are s block elements.
Both can form a monovalent cation.
Both are very reactive.
Both can form hydroxides when reacted with water.

Definition

Sodium: Sodium is a chemical element having the atomic number 11 and chemical symbol “Na”.

Potassium: Potassium is a chemical element having the atomic number 19 and chemical symbol “K”.

Period

Sodium: Sodium is in the period 3 of the periodic table.

Potassium: Potassium is in the period 4 of the periodic table.

Melting Point and Boiling Point

Sodium: The melting point is 97.79 °C and the boiling point is 882.8 °C.

Potassium: The melting point of potassium is 63.5 °C and the boiling point is 759 °C.

Electron Configuration

Sodium: Electron configuration of sodium is [Ne] 3s¹.

Potassium: The electron configuration of potassium is [Ar] 4s¹.

Valence Electron

Sodium: The valence electron of sodium is in the 3s orbital.

Potassium: The valence electron of potassium is in the 4s orbital.

Atomic Size

Sodium: Sodium atom is smaller than potassium atom.

Potassium: Potassium atom is larger than sodium atom.

Conclusion

Sodium and potassium are s block elements and belong to the group of alkali metals. They share many similarities because they are in the same group of the periodic table. The main difference between sodium and potassium is that sodium atoms are smaller than potassium atoms.

Reference:

1. “Sodium – Element information, properties and uses | Periodic Table.” Royal Society of Chemistry, Available here.
2. “Potassium.” Wikipedia, Wikimedia Foundation, 17 Jan. 2018, Available here.

Image Courtesy:

1. “Sodium metal chunks in oil” By W. Oelen – (CC BY-SA 3.0) via Commons Wikimedia
2. “Potassium” By Dnn87 – Self-photographed (CC BY 3.0) via Commons Wikimedia