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Option 3 : Lithium
The correct answer is Lithium.
- Lithium is the element that is atomic number 3 on the periodic table.
- This means each atom contains 3 protons.
- Lithium is a soft, silvery, light alkali metal that corrodes quickly in air denoted by the symbol Li.
- Properties of Lithium
- Lithium is the lightest metal and the lightest solid element at ordinary temperature and pressure.
- The density of the solid near room temperature is 0.534 g/cm3.
- This means it not only floats on water but is only about half as dense as it.
- It is so light, that it can even float on oil.
- It also has the highest specific heat capacity of a solid element.
- Element number 3 has the highest melting point and boiling point of the alkali metals.
- It is soft enough to cut with shears.
- Freshly cut metal is silver-coloured, with a metallic luster.
- However, moist air quickly corrodes the metal, turning it dull grey and finally black.
- Among its uses, lithium is used in medications for bipolar disorder, to make lithium-ion batteries, and to add red colour to fireworks.
- It's also used in glass and ceramics to make high-temperature lubricant grease.
- It is a coolant in breeder reactors and a source of tritium when atomic number 3 is bombarded with neutrons.
- Potassium
- Potassium is a chemical element with the symbol K and atomic number 19.
- Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force.
- Potassium metal reacts rapidly with atmospheric oxygen to form flaky white potassium peroxide in only seconds of exposure.
- Sodium
- Sodium is a chemical element with the symbol Na and atomic number 11.
- It is a soft, silvery-white, highly reactive metal.
- Sodium is an alkali metal, being in group 1 of the periodic table.
- Rubidium
- Rubidium is the chemical element with the symbol Rb and atomic number 37.
- Rubidium is a very soft, whitish-grey metal in the alkali metal group.
- Rubidium metal shares similarities to potassium metal and caesium metal in physical appearance, softness and conductivity.
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