What is Sodium Metal?
Sodium is defined as a chemical element of the alkali metal group (of Group 1 [Ia]) of the periodic table. The sodium element is a very soft and silvery-white metal. It is the most common alkali metal and the 6th most abundant element on Earth, comprising 2.8% of the crust of the Earth. It takes ace abundantly in nature in compounds, especially as common salt - the sodium chloride (NaCl), that forms the mineral halite and constitutes about 80% of the dissolved constituents of seawater.
The chemical formula of Sodium is given as Na and the Na chemical name is given as Sodium.
Properties of Sodium
The fastest reaction between the water and sodium is an example of intermolecular redox. Sodium reaction with air to form a sodium hydroxide film.
Principal Na Compounds
The sodium element is highly reactive and forms a wide range of compounds with nearly all organic and inorganic (negatively charged ions) anions. Its oxidation state is normally +1, and its single valence electron is colourless, yielding the colourless sodium cation (Na+). Compounds that are composed of sodium anion, Na−, have also been synthesized. The principal commercial sodium compounds are given as carbonate, sulfate, and chloride.
The most familiar and important sodium compound is common salt, or sodium chloride, NaCl. Most of the other sodium compounds are prepared either directly or indirectly from the sodium chloride, which takes place in natural brines, in seawater, and as rock salt. Excess quantities of sodium chloride are employed in other heavy (industrial) chemical production and being used directly for snow and ice removal as well, for water conditioning, and in food products.
Reactions of Sodium
Reaction with Air
Sodium is normally very reactive with air, and its reactivity is a result of the amount of water vapour in the air or the relative humidity. Also, the solid sodium’s corrosion by oxygen is accelerated by the presence of fewer amounts of impurities in the sodium. In ordinary air, though, the sodium metal reacts to create a sodium hydroxide coating, which can quickly absorb carbon dioxide from the air and form sodium bicarbonate. Since sodium metal does not react with nitrogen, it is normally held in a nitrogen setting (or in inert liquids such as naphtha or kerosene).
Significantly, it is more reactive in the air as a liquid than solid. And liquid can ignite at about 125 °C. Sodium metal softly burns in a relatively dry setting, emitting a thick white caustic smoke that can cause coughing and choking. The temperature of burning sodium rapidly increases to more than 800°C, and under such conditions, the fire is extremely difficult to extinguish. A special dry-powder fire extinguisher is required because sodium reacts with carbon dioxide, which is a common propellant in regular fire extinguishers.
Reaction with Nonmetals
In general, alkali metals react with the halogen gases, which is the degree of reactivity by decreasing with an increase in the atomic weight of the halogen. Sodium metal is no exception to this declaration. Under certain conditions of the reaction, halogen and sodium vapours react to form light (chemiluminescence). Halogen acids, like hydrochloric acid, vigorously react with sodium by yielding the sodium halides. These reactions are highly exothermic, with the reaction heats (energy is given off) of −76.2 and −71.8 kcal, respectively, for the reactions hydrochloric and hydrofluoric acids.
Sodium can be attacked by the other strong mineral acids to produce the corresponding salts. It also reacts with the nitric acid fumes at 15 °C to produce sodium nitrate and with sulfuric and acetic acids to produce sodium sulfate and sodium acetate. It reacts violently with molten sulfur to form polysulfides; it reacts with organic solutions of sulfur under more controlled conditions. Liquid tellurium and selenium both vigorously react with solid sodium to produce tellurides and selenides.
Organic Reactions
The organic reactions of sodium metal have been studied to a greater extent than those of any other alkali metals. Sodium metal reacts with anhydrous alcohols to produce respective alcoholates (or called alkoxides) as per the
Na + ROH → RONa + 1/2 H2,
where R is given as the alcohol’s organic portion (CH3CH2 for ethanol, R = CH3 for methanol, etc.). The reaction is the most vigorous one with methanol and decreases with increasing alcohol’s molecular weight. Sodium methoxide can be produced on an industrial scale by the reaction of sodium with excess methanol. Organic acids react with sodium metal to produce sodium salts.
Reaction with Metals
Sodium is completely miscible with the alkali metals down to it in the periodic table (rubidium, caesium, and potassium). A eutectic (which is an alloy that melts lower than its components) melting at a temperature of −10 °C is produced in the sodium-potassium system and is commercially known as NaK.
Its composition is around 78% of potassium, and it can be used as a heat-transfer fluid and as an organic reactant. The eutectics are produced in the sodium-caesium and the sodium-rubidium binary systems melt, at −30 °C and −4.5 °C, respectively. Sodium is a minor component with caesium and potassium of the ternary alloy NaKCs, melting at a temperature of −78 °C. This fluid is given as the lowest-melting liquid alloy yet to be isolated.
FAQs on Sodium
1. What is sodium and what are its key properties based on its position in the periodic table?
Sodium, with the chemical symbol Na, is an element located in Group 1 of the periodic table, making it an alkali metal. Its atomic number is 11, and its electronic configuration is [Ne] 3s¹. Due to the single valence electron in its outermost shell, sodium is highly reactive and readily loses this electron to form a stable positive ion (Na⁺). It is a soft, silvery-white metal with a low melting point.
2. Where is sodium found in nature?
Sodium is a highly reactive element and is never found in its pure, metallic form in nature. It is the 7th most abundant element in the Earth's crust. It occurs extensively in combined forms as various minerals, with the most common being sodium chloride (NaCl), which is found in seawater and as rock salt deposits. Other important sodium minerals include sodium carbonate (soda ash), sodium nitrate (Chile saltpetre), and borax.
3. What is the biological importance of sodium in the human body?
Sodium is an essential mineral for life. Its primary biological roles include:
- Maintaining fluid balance and blood pressure in the body.
- Enabling the proper functioning of nerves and muscles by transmitting nerve impulses.
- Regulating the body's acid-base balance (pH).
4. What are the common uses of metallic sodium and its compounds?
While metallic sodium has specific applications, its compounds are more widely used.
- Metallic Sodium (Na): Used as a strong reducing agent in the synthesis of organic compounds and certain metals. It is also used as a heat transfer fluid in some nuclear reactors.
- Sodium Chloride (NaCl): Used as table salt for flavouring and preserving food, and for de-icing roads in winter.
- Sodium Hydroxide (NaOH): A strong base used in the manufacture of soap, paper, and rayon.
- Sodium Bicarbonate (NaHCO₃): Also known as baking soda, it is used as a leavening agent in baking and in fire extinguishers.
5. Why is sodium metal stored under kerosene or oil?
Sodium is stored under kerosene or an inert mineral oil to prevent it from reacting with the environment. As an alkali metal, sodium is extremely reactive. It reacts vigorously with oxygen in the air to form sodium oxide and with moisture (water vapour) to form sodium hydroxide and hydrogen gas. This reaction with water is highly exothermic and can ignite the produced hydrogen gas. Kerosene provides a protective barrier, isolating the metal from air and moisture.
6. What is the difference between sodium (Na) and table salt (NaCl)?
This is a common point of confusion. Sodium (Na) is a chemical element, a highly reactive, soft, silvery metal that is unsafe to ingest. Table salt, on the other hand, is a chemical compound called sodium chloride (NaCl). It is formed when a sodium atom donates an electron to a chlorine atom, creating a stable ionic bond. While pure sodium is dangerous, sodium chloride is an essential nutrient and a stable crystalline solid.
7. How is metallic sodium extracted on a large scale?
Metallic sodium is commercially extracted using the Down's process. This method involves the electrolysis of molten sodium chloride (NaCl). To lower the high melting point of NaCl (around 801°C), calcium chloride (CaCl₂) is added. During electrolysis in the Down's cell, sodium ions (Na⁺) move to the cathode, gain an electron, and form liquid sodium metal, which is collected. Chloride ions (Cl⁻) are oxidized at the anode to form chlorine gas, which is also collected as a useful byproduct.
8. Why does sodium impart a characteristic golden-yellow colour when heated in a flame?
The golden-yellow colour is a result of an atomic phenomenon. When sodium or its compounds are heated in a Bunsen flame, the heat energy excites the outermost 3s electron to a higher energy level (e.g., the 3p orbital). This excited state is unstable, and the electron immediately falls back to its original ground state. In doing so, it releases the absorbed energy as light of a specific wavelength, which corresponds to the golden-yellow colour in the visible spectrum. This is the principle behind the flame test for sodium.
9. What happens to the body if sodium levels are too high or too low?
Maintaining a proper balance of sodium is crucial for health.
- High Sodium (Hypernatremia): Excess sodium in the blood can pull water out of your cells, leading to dehydration. It can cause intense thirst, high blood pressure, and in severe cases, confusion, muscle twitching, and seizures. This condition puts a strain on the heart and kidneys.
- Low Sodium (Hyponatremia): Insufficient sodium can be caused by excessive water intake or certain medical conditions. It causes water to move into cells, leading to swelling. Symptoms can include nausea, headache, fatigue, and muscle cramps. Severe hyponatremia can be life-threatening.
10. How does sodium react with water, and why is the reaction so vigorous?
Sodium reacts rapidly and exothermically with water to produce sodium hydroxide (NaOH) and hydrogen gas (H₂). The chemical equation is: 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g). The reaction is vigorous because:
- Sodium is a highly electropositive alkali metal with a very low ionisation enthalpy, meaning it readily loses its valence electron.
- The reaction releases a large amount of heat (it is highly exothermic), which often melts the sodium metal and can ignite the flammable hydrogen gas produced, causing a small explosion or fire.
