1.12. The Alkaline Earth Metals and the Oxygen Group

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The alkaline earth metals

The alkaline earth metals are in group 2 of the periodic table.

The alkaline earth metals are:

Beryllium, Be
Magnesium, Mg
Calcium, Ca
Strontium, Sr
Barium, Ba
Radium, Ra (don't confuse with radon, Rn!)

Alkaline earth metals have two valence electrons. Example: ₄Be

	K	L
4p⁺	2e^–	2e^–

The most reactive alkaline earth metal

The the further away from the nucleus, the easier the valence electrons are lost.

In radium: Valence electrons in the 5th shell ⇒ very easily lost!
In beryllium: Valence electrons in the 2nd shell ⇒ not as easily lost ⇒ not as reactive.

The oxygen group (chalcogens)

The oxygen group (the chalcogens) are in group 16 of the periodic table.

The chalcogens are:

Oxygen, O
Sulfur, S
Selenium, Se
Tellurium, Te
Polonium, Po
Livermorium, Lv

Chalcogens have six valence electrons. Example: ₁₆S

	K	L	M
16p⁺	2e^–	8e^–	6e^–

The metal character increases downwards in the oxygen group

Oxygen

Gas in room temperature, O₂(g)

Sulfur

Yellow, solid, S₈

Selenium

Non-metal, essential trace element

Tellurium

Metalloid, used in iron alloys

Polonium

Radioactive metal found in uranium-rich ores

Livermorium

Synthetic. Properties: ?

Burning magnesium in air (oxygen gas)

Magnesium burns with a white flame.

What happens? The magnesium is oxidized:

Mg	K	L	M
12p⁺	2e^–	8e^–	2e^–

+ energy →

Mg²⁺	K	L
12p⁺	2e^–	8e^–

+ 2e^–

At the same time, oxygen is reduced:

O	K	L
8p⁺	2e^–	6e^–

+ 2e^– →

O^2–	K	L
8p⁺	2e^–	8e^–

+ energy

Word equation:

Magnesium + oxygen gas → magnesium oxide

Chemical equation:

2Mg + O₂ → 2MgO