8.1 Group 2 Flashcards
What type of elements are in group 2
Metals
Often referred to as the alkaline earth metals
How are they found on Earth
Found in stable compounds such as calcium carbonate
How many electrons does an element in group 2 have in its outer shell
2
What is the most common type of reaction in group 2
Redox
Each metal atom is oxidised losing two electrons to form a 2+ ion with the electron configuration of a noble gas
Group 2 element called the reducing agent as it has reduced another species
What is the reducing agent
The element which has caused another to be reduced
What do group 2 elements form when they react with oxygen
Metal oxides with the general formula MO
What do group 2 elements form when they react with water
Alkaline hydroxides with the general formula M(OH)2, and hydrogen gas
Reaction between magnesium and water
React very slowly but the reaction becomes more and more vigorous with metals further down the group - reactivity increases down the group
Pattern of reactivity in group 2
Increases going down the group
Group 2 and acid redox reactions
Form a salt and hydrogen gas
Metal + Acid -> Salt + Hydrogen
Why does reactivity increase down group 2
The ionisation energies decrease down the group as the attraction between the nucleus and the outer electrons decreases as a result of increasing atomic radius and increasing shielding.
The formation of +2 ions from gaseous atoms requires the input of two ionisation energies:
M(g) -> M+(g) + e-
M+(g) -> M2+(g) + e-
Group 2 reactions with water
Release hydroxide ions OH- and forming alkaline solutions of the metal hydroxide
Are group 2 hydroxides soluble in water
Only slightly
When the solution becomes saturated, any further metal and hydroxide ions will form a solid precipitate
How does the solubility of the hydroxides change down a group
Solubility increases down the group so resulting solutions contain more OH- ions and are more alkaline
