Introduction
Rubidium is an alkali metal present in group number 1 of the periodic table.
- Its atomic number is 37 whereas its atomic mass is 85.46.
- Rubidium has 37 electrons.
- It has 37 protons and 48 neutrons in its nucleus.
- Rubidium is represented by the symbol “Rb”.
Naming and History
The name of rubidium comes from the Latin word “Rubidius” which means “deep red”. The atomic spectra of rubidium showed ruby red lines, that were never seen before. It was named after that spectrum.
Robert Bunsen and Gustav Kirchhoff
In 1861, Robert Bunsen and Gustav Kirchhoff discovered rubidium, in Heidelberg, Germany, by utilizing spectroscopy. Bunsen and also Kirchhoff placed different salts in the fire of the recently invented Bunsen burner.
They saw colored lines in each of the spectra they took. They discovered that these colored lines were unique to whichever substance was burnt. The lines in a range were a method of ‘fingerprinting’ an element (known or not known).
Bunsen extracted rubidium metal from its chloride salt by electrolysis. He found that the rubidium was a lot more electropositive than potassium and decomposed water releasing hydrogen.
A sample of pure rubidium was obtained in 1928.
Occurrence of Rubidium
It is estimated that rubidium is the 16th most abundant element in Earth’s crust. Although it does not have its own minerals. It never occurs as a free element. It is present in other minerals such as carnallite, lepidolite, etc. Trace amounts are also found in leucite, zinnwaldite, etc.
Large amounts of rubidium are obtained as a byproduct of lithium in lithium refining, nowadays.
Properties of Rubidium
Rubidium is a silvery-white, metallic, soft alkali metal. It is considered among one of the most electropositive elements. It exists as solid at room temperature but can easily melt on a hot day as its melting point is 39.31 °C.
The boiling point of rubidium is 688°C. It has a density of 1.53 grams per cubic centimeter. Rubidium ignites spontaneously in the air and can vigorously react with water even with ice. It liberates hydrogen and is set on fire immediately.
Rubidium, like other alkali metals, forms amalgams with mercury. On burning, it produces a yellowish-violet flame.
Rubidium in Biological Systems
There is no known significant role of rubidium in living organisms. However, some researches show its usage in the treatment of depression. Patients with kidney dialysis tend to be depressed and show reduced levels of rubidium.
Uses of Rubidium
Rubidium has not a wide range of uses. But some of them are given:
- It is used to remove traces of oxygen and residual gases from vacuum tubes.
- Rubidium is used in making special types of glasses and manufacturing photocells.
- Rubidium is used in fireworks, pyrotechnics to give them purple color.
- It is used in ceramics.
- The compound of rubidium, iodine, silver has characteristic electrical properties and is used in thin-film batteries.
- It can be easily ionized so used in ion engines of space vehicles.
- It is used as a working fluid for vapor turbines and thermoelectric generators.
Isotopes of Rubidium
There are almost 29 known isotopes of rubidium. Two naturally occurring isotopes are Rb- 85 and Rb- 87.
- Rb- 87 is slightly radioactive and used in locating tumors in the brain and in the precise dating of rocks.
Multiple Choice Questions (MCQs) on Rubidium
- What is the atomic number of Rubidium?
- A) 37
- B) 48
- C) 85.46
- D) 39.31
- Answer: A
- Who discovered rubidium using spectroscopy in 1861?
- A) Robert Bunsen
- B) Gustav Kirchhoff
- C) Both A and B
- D) Antoine Lavoisier
- Answer: C
- Why was rubidium named “rubidius”?
- A) It means “deep red” in Latin, reflecting its color.
- B) It was named after its discoverer, Robert Bunsen.
- C) It was associated with ruby gemstones.
- D) The atomic spectra showed ruby red lines.
- Answer: D
- How was rubidium metal extracted by Robert Bunsen?
- A) From its oxide salt by distillation
- B) From its chloride salt by electrolysis
- C) Through reduction with hydrogen gas
- D) By fusion with potassium
- Answer: B
- Which element is considered more electropositive than rubidium?
- In what form is rubidium obtained in lithium refining?
- A) Pure metal
- B) Rubidium chloride
- C) Rubidium oxide
- D) Rubidium amalgam
- Answer: D
- What is the estimated abundance of rubidium in Earth’s crust?
- A) 5th most abundant
- B) 10th most abundant
- C) 16th most abundant
- D) 20th most abundant
- Answer: C
- At what temperature does rubidium melt?
- A) 20.5°C
- B) 39.31°C
- C) 100°C
- D) 688°C
- Answer: B
- What is the primary use of rubidium in vacuum tubes?
- A) Catalyzing chemical reactions
- B) Enhancing conductivity
- C) Removing residual gases
- D) Creating colored flames
- Answer: C
- Which alkali metal forms amalgams with mercury?
- A) Lithium
- B) Sodium
- C) Rubidium
- D) Potassium
- Answer: C
- What is the color of the flame produced by burning rubidium?
- A) Red
- B) Blue
- C) Yellowish-violet
- D) Green
- Answer: C
- In which biological condition is rubidium suggested for treatment?
- A) Diabetes
- B) Hypertension
- C) Depression
- D) Anemia
- Answer: C
- Which isotope of rubidium is used in locating tumors in the brain?
- A) Rb-85
- B) Rb-87
- C) Rb-88
- D) Rb-86
- Answer: B
- How many known isotopes does rubidium have?
- A) 20
- B) 29
- C) 42
- D) 50
- Answer: B
- What unique property of Rb-87 makes it useful in precise rock dating?
- A) It is a stable isotope
- B) It is radioactive
- C) It emits visible light
- D) It has a long half-life
- Answer: B
- In which industry is rubidium used as a working fluid for vapor turbines?
- A) Aerospace
- B) Electronics
- C) Energy
- D) Pharmaceuticals
- Answer: C
- What is the color imparted to fireworks by rubidium compounds?
- A) Red
- B) Blue
- C) Green
- D) Purple
- Answer: D
Summary: Rubidium – Occurrence, Properties, Uses, and Isotopes
Rubidium, an alkali metal in group 1 of the periodic table, is characterized by its atomic number 37 and atomic mass of 85.46. Its symbol is “Rb,” and it comprises 37 electrons, with a nucleus containing 37 protons and 48 neutrons.
Naming and History: The name “Rubidium” originates from the Latin word “Rubidius,” meaning “deep red,” inspired by the ruby red lines observed in its atomic spectra. Discovered in 1861 by Robert Bunsen and Gustav Kirchhoff using spectroscopy, rubidium was extracted from its chloride salt through electrolysis. Its electropositivity and hydrogen-releasing properties distinguished it from potassium.
Occurrence: While not freely occurring in nature, rubidium is estimated as the 16th most abundant element in Earth’s crust. It is found in minerals like carnallite and lepidolite, often obtained as a byproduct during lithium refining.
Properties: Rubidium exhibits silvery-white metallic properties, presenting as a soft alkali metal at room temperature. With a low melting point of 39.31°C and a boiling point of 688°C, it ignites spontaneously in air and reacts vigorously with water. It forms amalgams with mercury and produces a yellowish-violet flame when burned.
Biological Systems: While rubidium doesn’t play a significant role in living organisms, some research suggests its potential use in depression treatment, particularly in kidney dialysis patients.
Uses: Rubidium finds applications in various fields:
- Removing oxygen and residual gases from vacuum tubes.
- Manufacturing special glasses and photocells.
- Adding a purple color to fireworks and pyrotechnics.
- Utilization in ceramics and thin-film batteries.
- Ionization for ion engines in space vehicles.
- Working fluid in vapor turbines and thermoelectric generators.
Isotopes: Rubidium has approximately 29 known isotopes, with Rb-87 being slightly radioactive. Rb-87 is employed in locating brain tumors and precise rock dating.
In conclusion, rubidium, with its unique properties and applications, contributes to diverse fields, from technology to healthcare. Understanding its characteristics enhances our knowledge of the periodic table and its elements.