8.1 Group 2
No description yet. This curated deck is ready for daily study.
Card preview (19)
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
How to show the trend that the solubility of the hydroxides in water increases down the group
• Add spatula of each Grp 2 oxide to water in test tube • Shake mixture, Will have saturated solution of metal hydroxide • Measure pH. Alkalinity will increase down group
What are the uses of group 2 compunds
Agriculture Medicine
Group 2 compounds and agriculture
Calcium hydroxide added to fields as lime by farmers to increase pH of acidic sols Neutralises the soil forming neutral water
Group 2 compounds in medicine
Often used as anatacids for treating acid indigestion Many indigestion tablets use magnesium and calcium carbonates Acid in stomach mainly HCl so is neutralised