Strontium (Sr)

Strontium properties

Atomic number

38

Atomic mass

87.62 u

Category

Alkaline earth metal

Group

2

Period

5

Block

s-block

State at room temp.

Solid

Electronegativity

0.95

Melting point

1,050 K (776.8 °C)

Boiling point

1,650 K (1,376.8 °C)

Density

2.64 g/cm³

Valence electrons

2

Common charges

+2

Oxidation states

+2

Atomic radius

249 pm

Ionization energy

5.695 eV

Electron affinity

—

Radioactive

No, has stable isotopes

Discovered

1790

Strontium electron configuration

The electron configuration of Strontium (Sr) is [Kr] 5s2. Its 38 electrons are arranged in shells as 2, 8, 18, 8, 2.

Protons, neutrons and electrons in Strontium

A neutral Strontium atom has 38 protons and 38 electrons. Most Strontium atoms have about 50 neutrons: the atomic mass rounded to 88, minus the atomic number 38.

Neutrons are approximate: atoms of the same element can have different numbers of neutrons (isotopes). Atomic number and mass

How many valence electrons does Strontium have?

2

Strontium has 2 valence electrons in its outermost shell, shell 5. These are the electrons involved in chemical bonding.

See every element: Periodic table with valence electrons

Strontium orbital diagram

Each box is an orbital that holds up to two electrons with opposite spins (↑↓). The inner shells are the same as the noble gas in brackets. How to write electron configurations

Molar mass of Strontium

87.62 g/mol

One mole of Strontium atoms (6.022 × 10²³ atoms) has a mass of 87.62 grams. Use this value to convert between grams and moles.

Strontium facts

• Radioactive strontium-90 from nuclear fallout is dangerous because the body treats strontium like calcium and builds it into bones.
• Strontium isotope ratios in ancient teeth reflect the local rocks where a person grew up, helping archaeologists trace past migrations.
• Strontium (Sr) has atomic number 38 and is a solid at room temperature. It was discovered in 1790.

Position in the periodic table

Strontium is element 38, in period 5 and group 2 of the periodic table, in the s-block.

All alkaline earth metals

Uses of Strontium

Strontium compounds give fireworks and emergency flares their bright crimson-red color. Strontium aluminate is the basis of modern glow-in-the-dark pigments for safety signs and watch dials, and strontium ferrite is used to make inexpensive permanent magnets for small motors and loudspeakers. Strontium was also once added to the glass of color TV picture tubes to block X-rays.

Who discovered Strontium?

In 1790 Adair Crawford and William Cruickshank recognized that a mineral from the lead mines near Strontian, Scotland, contained a new 'earth'. Humphry Davy first isolated the metal by electrolysis in 1808.

Where does the name come from?

Strontium is named after Strontian, a village in the Scottish Highlands. A new mineral from its lead mines, later called strontianite, led to the discovery of the element in the 1790s.

Discovery timeline