Alkali Metals
The most reactive metals in the periodic table. All elements in this group have one electron in their outer shell, making them extremely active in chemical reactions.
Read in glossaryLithium, sodium, and potassium are so light that they float on water (before they explode).
Cesium is used in atomic clocks. Cesium clocks are so accurate that they lose only 1 second in 300 million years.
Francium is the rarest naturally occurring element on Earth. At any moment, only about 30 grams exist on the planet.
Lithium is a key component of lithium-ion batteries that power smartphones, laptops, and electric vehicles.
Sodium chloride (table salt) is one of the most important compounds for humanity, known since ancient times.
All elements have ns¹ configuration — one electron in the outer s-orbital.
Most reactive metals. Reactivity increases with atomic number.
All alkali metals react vigorously with water
2Na + 2H₂O → 2NaOH + H₂↑| Element | Z | Mass u | M.P. °C | B.P. °C | ρ г/см³ | EN |
|---|---|---|---|---|---|---|
Li Lithium | 3 | 7.00 ▼ | 181 ▲ | 1342 ▲ | 0.53 ▼ | 0.98 ▲ |
Na Sodium | 11 | 22.99 | 98 | 883 | 0.97 | 0.93 |
K Potassium | 19 | 39.10 | 64 | 759 | 0.86 | 0.82 |
Rb Rubidium | 37 | 85.47 | 39 | 688 | 1.53 | 0.82 |
Cs Cesium | 55 | 132.91 | 29 | 671 ▼ | 1.93 ▲ | 0.79 |
Fr Francium | 87 | 223.00 ▲ | 27 ▼ | 677 | 1.87 | 0.70 ▼ |
The name comes from the Arabic word 'al-qaly' (القلي), meaning 'ash'. Arab alchemists obtained potash (potassium carbonate) from plant ashes. When dissolved in water, it forms lye — a caustic substance with high pH.
Sir Humphry Davy, using a new electrolysis method, isolated potassium (from potash), sodium (from soda), and barium.
Robert Bunsen and Gustav Kirchhoff discovered cesium (1860) and rubidium (1861) by their unique spectral lines.
Marguerite Perey, Marie Curie's assistant, discovered francium as a decay product of actinium.
Discovered K, Na, Ca, Mg, Sr, Ba, B by electrolysis
Discovered Cs, Rb with Kirchhoff by spectroscopy
Discovered francium (1939)