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Rubidium is one of the most highly reactive elements of the periodic table. The chemical element has the atomic number 37 and is recognized by the symbol Rb.
- Rubidium bursts into flames as soon as it comes in contact with air and reacts violently with ice and water.
- Rb is a silvery-white and extremely soft metal that cannot produce minerals of its own.
- It forms an alloy with potassium, caesium, sodium, and gold.
- The density of rubidium is higher than that of water, which is why it easily sinks, unlike other alkali metals.
- It is recognized as a lithophile metallic element.
- You can use this element in medical imaging equipment and night-vision devices.
Key Terms: Rubidium, Alkali Metals, Properties of Rubidium, Uses of Rubidium, Atomic Number, Metal, Periodic Table, Rubidium Structure
What is Rubidium?
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Rubidium (Rb) is a chemical element in the alkali metal group 1 of the periodic table. It consists of two isotopes: a 72% stable 85Rb isotope and a 28% radioactive 87Rb isotope.
- The rubidium has many similarities with the potassium and the caesium metals in terms of physical appearance, softness and conductivity.
- It undergoes exothermic reactions when stored under atmospheric oxygen.
- The word rubidium is derived from the Latin word ‘rubidus’, which means deepest red.
- It was discovered by German chemists Robert Bunsen and Gustav Kirchhoff in 1861 from the mineral lepidolite.
- The element is used in the fireworks to give a purple-red colour.
- The electron configuration of rubidium is 1s22s22p63s23p64s23d104p65s1.
| Class 11 Chemistry Related Concepts | ||
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| Ammonia | Sandmeyer Reaction | Enantiomers |
| Oxidizing Agent | Alliphatic Hydrocarbons | Mitsunobu Reaction |
Rubidium Structure
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Rubidium atoms have 37 electrons. The electronic shell structure of Rubidium is [2, 8, 18, 8, 1]. The atomic radius of the element is 265 pm with an atomic volume of 55.788381201cm3.
- It has a valency of 1, comprising one electron in the outermost shell (5s1).
- The nucleus of the element contains 37 protons (red) and 48 neutrons, which are indicated by a blue-coloured electron.
- 37 green electrons are responsible for binding the nucleus, with relatively unstable electrons in the outer shell.
- Rubidium forms a body-centered cubic crystal structure with a radius of 0.562 nm
Rubidium
Properties of Rubidium
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The properties of rubidium is divided into physical and chemical properties which are as follows:
Physical Properties of Rubidium
The important physical properties of Rubidium are as follows:
- The atomic mass of rubidium is 85.4678 g/mol.
- The density of the element is 1.53 g/cm3
- The melting point and boiling point of rubidium is 39.30oC or 102.74oF or 312.45 K and 688oC or 1270oF or 961K, respectively.
- The key isotopes of the element are 85Rb and 87Rb
- Rubidium retains its solid-state at the temperature of 20oC
- It gives out a flame of yellowish violet in color.
The physical properties of rubidium are tabulated below:
| Category | Data |
|---|---|
| Group | 1 |
| Period | 5 |
| Block | s |
| Atomic number | 37 |
| State at 20°C | Solid |
| Electron configuration | [Kr] 5s1 |
| Melting point | 39.30°C, 102.74°F, 312.45 K |
| Boiling point | 688°C, 1270°F, 961 K |
| Density | 1.53 |
| Relative Atomic Mass | 85.468 |
Chemical Properties of Rubidium
The chemical properties of rubidium are as follows:
- When rubidium reacts with halogens, it will form compounds like rubidium fluoride, rubidium chloride, rubidium bromide, and rubidium iodide.
- On undergoing hydrolysis, it will form rubidium hydroxide and hydrogen.
- When exposed to air, rubidium forms oxides like rubidium monoxide Rb2O, Rb6O, and Rb9O2.
- When the element reacts with water, it forms a solution of rubidium hydroxide (RbOH) and hydrogen, which ignites spontaneously.
Uses of Rubidium
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Various applications of rubidium are as follows:
- Following the magnetohydrodynamic principle, rubidium is used in a thermoelectric generator where heated ions pass through a magnetic field.
- The element is used to produce superoxide by burning in the presence of oxygen and to make a special type of glass.
- Laser cooling and bose-einstein condensation commonly use vaporized rubidium, which is one of the isotopes 87Rb.
- It helps remove the remaining gases from the vacuum tubes because of its efficacy in easily bonding with other gases.
- The compound is used in myocardial treatment and studies.
- Rubidium has a rich Feshbach spectrum, 85Rb, used for cold atom applications that need tunable interactions.
- Photocathodes of photomultiplier tubes are used in radiation detector devices, non-vision devices, and medical imaging equipment.
- It is used as vapour in the atomic magnetometer, as a working fluid in vapour turbines, as a component of the photocell, and as a getter in the vacuum tubes.
- The manufacture of ceramics and glasses use rubidium salt.
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Things to Remember
- Rubidium has a low melting point as it melts easily on being slightly warmer.
- It is treated as a toxic element by scientists as it bursts out into flames due to the presence of humidity in the air.
- The element tends to form more positive ions easily, making it more electropositive than potassium.
- It should be stored in an inert gas atmosphere in mineral oil as it is highly reactive with air and water.
- Rubidium is used in ion engines for spacecraft because of its easy ionization.
Sample Questions
Ques: What makes rubidium so expensive? (2 marks)
Ans: Rubidium is one of the rarest elements and does not have many commercial uses. It has to go through a difficult and lengthy process to break the chemical bond. It can result in the production of the metal in its pure state.
Ques: Which process is used to extract rubidium? (2 marks)
Ans: Electrolysis is used to extract rubidium from the environment. In order to study the properties of rubidium, 150kg of lepidolite ore is required to extract enough rubidium. Initially, the use of rubidium was limited to chemical reactions, electronic appliances, and research.
Ques: Why is the extraction of pure rubidium difficult? (2 marks)
Ans: Rubidium is usually found combined with cesium and other alkali metals. The similarity in the property of the alkali metals makes it difficult to separate rubidium from other alkali metals.
Ques: What is the structure of rubidium? (2 marks)
Ans: Rubidium has a cubic and crystal structured body with silver color. A Rubidium atom has 37 electrons and the electron cell structure is [2, 8, 18, 8, and 1]. There are 48 neutrons. The mass number is 85. The atomic term symbol is 2S1/2.
Ques: What type of bonds does rubidium have? (2 marks)
Ans: Rubidium falls under the category of group 1 elements which are recognized as alkali metals. Rubidium, being the second most electropositive element on the periodic table, easily gives up its electron to form an ionic bond. It also shows violent reactivity in the presence of air and water.
Ques: Is rubidium an active metal? (2 marks)
Ans: Rubidium is one of the most active alkali metals. It is a soft and silvery-white metallic element of group 1. The other active elements that belong to group IA and IIA are lithium, sodium, potassium, cesium, calcium, strontium, and barium.
Ques: Where does rubidium occur? (3 marks)
Ans: Minerals such as pollucite, leucite, zinnwaldite, carnallite, and lepidolite carry a significant amount of rubidium in them. Seawater and mineral springs also have rubidium in them. About 35 to 75ppm of rubidium is found on the earth. Rubidium 85 and rubidium 87 are the naturally occurring isotopes of rubidium. While refining lithium from lepidolite, the byproduct thus produced is known as rubidium. Rubidium chloride is produced by using sodium or chloride.
Ques: How can rubidium affect health? (3 marks)
Ans: The health hazards of rubidium are:
- When consumed, it is moderately toxic
- It will cause thermal burns when it ignites
- It causes eye and skin burns when if overexposed
- Overexposure can also cause hyper irritation, skin ulcer, nervousness, ataxia, and failure to gain weight.
Ques: What are some of the common uses of rubidium? (5 marks)
Ans: Some of the common uses of rubidium are:
- It is used in atomic clock
- Rubidium is also used in the photocells which converts light energy to electrical energy
- For detecting ischemia.
- Laser cooling and bose-einstein condensation commonly use vaporized rubidium which is of the isotopes 87Rb.
- Rubidium has a rich Feshbach spectrum, 85Rb is used for cold atom applications that need tunable interactions.
- Helium 3 gas is also polarized by rubidium.
- Photocathodes of photomultiplier tubes are used in radiation detector devices, non-vision devices, and medical imaging equipment. They are coated with rubidium-cesium-antimony.
Ques: What is the appearance of rubidium? (2 marks)
Ans: Rubidium is a soft, silvery-white metal that belongs to the alkali group. It is the second-highest electropositivity and alkaline element. Since it is a highly reactive element, it ignites spontaneously in the air and explodes violently in contact with water, releasing hydrogen.
Ques: Why is rubidium stored under oil? (2 marks)
Ans: Rubidium is stored in dry mineral oil. This is particularly true for the alkali metals that are heavier, such as caesium, rubidium, and potassium. Alkali metals are kept under oil to stop these potentially harmful reactions. The metals are kept from contacting the air by the oil, which serves as a physical barrier.
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