Chapter 4 - Inorganic chemistry and the Periodic table (L) Flashcards
What is the definition of first ionisation energy?
The energy required to remove an electron from each atom in one mole of atoms in gaseous state
What is the definition of second ionisation energy?
The energy required to remove an electron from each 1+ ion in one mole of 1+ ions in gaseous state
What is the base cause of a high or low ionisation energy?
A high or low electrostatic attraction between the nucleus and outermost electron
What is electron shielding, and what is its effect on ionisation energy?
The idea that inner electrons shield the outer electrons from the electromagnetic pull of nucleus, weakening their attraction.
This hence decreases ionisation energy, as it is not as difficult to remove the outer electron
What are the 3 main factors to consider when explaining trends in ionisation energy?
- Nuclear charge
- Number of shells
- Electron shielding
What is the trend in reactivity down group 2?
Reactivity increases down the group, as less energy is required to remove the 2 outer electrons as you go down the group (first and second ionisation energy)
What is the trend in the vigorousness of reactions down group 2?
As you go down group 2, the reactions become more vigorous
What happens between group 2 elements and oxygen even without heating?
A slow reaction occurs, in which a surface coating of oxygen forms around the element, helping prevent further reaction
How is barium often stored and why?
Because it is the most reactive, it is often stored under oil to keep it reacting with oxygen and water vapour in the air
What is the general formula for group 2 reactions with oxygen? (M = group 2 element)
2M(s) + O2(g) -> 2MO(s)
What is the general formula for group 2 reactions with chlorine? (M = group 2 element)
M(s) + Cl2(g) -> MCl2
What is effervescence?
Bubbles in a liquid (fizz)
What is seen in the reactions with group 2 elements with water as you go down the group?
Increasing effervescence
What is the general formula for group 2 reactions with water? (M = group 2 element)?
M(s) + 2H2O(l) -> M(OH)2(aq) + H2(g)
What is the exception to the general formula for group 2 reactions with water?
Calcium, which forms a solid rather than aqueous hydroxide- Ca(OH)2 (s)
What is the formula for when Mg is heated in steam?
Mg(s) + H2O(g) -> MgO(s) + H2(g)
Why is hydrogen burned as it leaves the tube?
So it forms H2O, so there is not a highly flammable gas floating around in the lab
Why is it not a good idea to use water to put out a magnesium fire?
Because the magnesium will react with the water, feeding the fire more oxygen and releasing flammable hydrogen gas, which will further feed the fire
What type of oxides are group 2 oxides?
Basic oxides
What are basic oxides?
Oxides that can react with water to form alkalis
What is the general formula for group 2 oxides reacting with water?
MO(s) + H2O(l) -> M(OH)2 (aq)
What is the trend in solubility down group 2?
As you go down the group, solubility increases
What is the trend in the alkalinity of solution produced down group 2?
As you go down the group the pH (alkalinity) increases
What can be used to test for carbon dioxide?
Calcium hydroxide (limewater)- goes milky as a white precipitate forms. Calcium reacts with CO2 to form calcium carbonate (white precipitate)
What is milk of magnesia and what does it do?
Magnesium hydroxide- it reacts with HCl in the stomach, neutralising it
What do all group two oxides and hydroxides react with acids to form?
Salts and water (neutralisation reactions)
Example of how group 2 hydroxides are used in agriculture
Calcium hydroxide is used to neutralise excess acidity in soil
What is the solubility of group 2 nitrates and chlorides?
All group 2 nitrates and chlorides are soluble
What is the trend in the solubility of group 2 sulfates?
The solubility of group 2 sulfates decreases down the group
What solubility is magnesium sulfate classed as?
Magnesium sulfate is soluble
What solubility is calcium sulfate classed as?
Calcium sulfate is slightly soluble
What solubility is strontium and barium sulfate classed as?
Insoluble
How can you use barium ions to test for sulfate ions?
A solution containing barium ions can be added, and any sulfate ions will react with the barium ions to form a white precipitate of barium sulfate
Why is an acid also added alongside the barium ions to test for sulfate ions?
To prevent barium ions reacting with carbonate ions, which would also form a white precipitate
How and why are barium meals used?
Solutions containing barium ions are poisonous to humans, however barium sulfate is insoluble so not poisonous (as the ions cannot move).
Barium meals are used to make soft tissues show up more clearly in x-rays
What is thermal stability?
The measure of the extent to which a compound decomposes when heated
What is the difference in thermal stability between group 1 and 2?
Group 1 compounds are more thermally stable than group 2 compounds
What are 2 reasons why group 1 compounds are more thermally stable than group 2 compounds?
- Group 2 cations have double the charge
- The ionic radius of group 2 cations is smaller (in the same period)
What is the trend in ionic radius of group 2 cations?
As you go down the group, ionic radius increases
What do all group 1 and 2 nitrates decompose to when heated?
Nitrites (lesser decomposition) or oxides (greater decomposition)
What are the brown fumes that are given off during the decomposition of nitrates?
Nitrogen dioxide
What does brown fumes not being given off indicate?
Lesser decomposition
What does brown fumes being given off indicate?
Greater decomposition
What is the word equation for lesser decomposition of nitrates?
Metal nitrate -> metal nitrite + oxygen
What is the word equation for greater decomposition of nitrates?
Metal nitrate -> metal oxide + nitrogen dioxide + oxygen
What type of decomposition occurs in group 2 nitrates, and what does this mean brown fumes wise?
All group 2 nitrates have greater decomposition, which means they will give off brown fumes
What type of decomposition occurs in group 1 nitrates, and what does this mean brown fumes wise?
Group 1 nitrates have lesser decomposition, which means they will not give off brown fumes.
EXCEPT FOR ONE EXCEPTION- LITHIUM NITRATE
What is the one exception to group 1 nitrates decomposition and why?
Lithium nitrate- this is because it is the smallest group 1 cation
What are the two possibilities of decomposition of group 1 and 2 carbonates?
They either don’t decompose, or decompose to oxides and give off carbon dioxide
What is the word equation for the decomposition of carbonates?
Metal carbonate -> metal oxide + carbon dioxide
Do group 2 carbonates decompose?
Yes. All group 2 carbonates decompose to a metal oxide, giving off carbon dioxide
Do group 1 carbonates decompose?
No. Group 1 carbonates do not decompose.
EXCEPT FOR ONE EXCEPTION- LITHIUM CARBONATE
What is the one exception to the decomposition of group 1 carbonates and why?
Lithium carbonate- this is because it is the smallest group 1 cation
What observations can be made for the decomposition of carbonates and why?
No observations can be made.
Both carbonate and oxides are white solids, and carbon dioxide is given off, which is colourless
Why does a greater charge on the cations lead to a lower thermal stability?
Because a greater charge will result in a higher level of electron distortion, making it more unstable
Why does a smaller size result in a higher level of distortion?
It means the cation will have a higher charge density, which will result in a higher level of electron distortion, making it more unstable