Element 12
Magnesium
Alkaline earth
Magnesium (Mg) is in the s-block of the periodic table — group 2, period 3.
Magnesium is a chemical element with symbol Mg and atomic number 12.
Key data
- Atomic number
- 12
- Atomic mass
- 24.305 u
- Group / Period
- 2 / 3
- Block
- s-block
- Phase at STP
- Solid
- Density
- 1.738 g/cm³
- Melting point
- 649.9 °C
- Boiling point
- 1089.8 °C
- Electron configuration
- [Ne] 3s2
Periodic table block
Magnesium is in the s-block (group 2, period 3). Elements land in the s-block when their highest-energy electrons fill an s subshell — this includes hydrogen, helium, and the reactive metals on the far left of the table.
New to this? Periodic table blocks explained: s, p, d, and f
Common uses
- •Lightweight alloys
- •Camera flashes
- •Chlorophyll
Discovery
Year: 1755
Discovered by: Joseph Black
Frequently asked questions
What is the atomic number of Magnesium?
Magnesium has atomic number 12. Its symbol is Mg and its atomic mass is 24.305 u.
What category of element is Magnesium?
Magnesium is classified as alkaline earth. It sits in group 2, period 3 of the periodic table.
What block of the periodic table is Magnesium in?
Magnesium is in the s-block (group 2, period 3). Its highest-energy electrons occupy the s subshell — you can see this in its electron configuration, [Ne] 3s2.
What is Magnesium used for?
Common uses of Magnesium include: Lightweight alloys, Camera flashes, Chlorophyll.
When was Magnesium discovered?
Magnesium was discovered in 1755 by Joseph Black.
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