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What is the electron configuration pattern shared by alkaline-earth metals?

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A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — alkaline-earth metal Modern version of the periodic table of the elements (printable).

The atoms of all alkaline-earth metals share a common electronic structure characterized by a pair of s electrons in their outermost orbital, which sits outside a stable, complete noble gas configuration.1

This pattern can be represented by the general notation $n s^{2}$ , where n represents the principal quantum number of the outermost shell. Examples of this configuration for the group members include:1

Beryllium (Be): [He]2s²1
Magnesium (Mg): [Ne]3s²1
Calcium (Ca): [Ar]4s²1
Strontium (Sr): [Kr]5s²1
Barium (Ba): [Xe]6s²1
Radium (Ra): [Rn]7s²1

Because these two outermost electrons are relatively easy to remove, the chemistry of these elements is dominated by the formation of doubly charged M²⁺ ions, resulting in a characteristic oxidation state of +2.1