Chapter 4 Flashcards
What happens to ionisation energy as you go down the group?
It decreases
Why does the ionisation energy decrease as you go down the group?
- Each element has an extra electron shell
- Extra shells shield attraction from the nucleus
- Outer electrons are further away from the nucleus
As ionisation energy decreases down the group, why does this mean that the reactivity in group 1 increases as you go down the group?
It is easier for the elements to lose their outer electron when they react and form a +1 ion.
What ions do group 2 elements form?
+2 ions
When group 2 elements react with water, what do they form?
Metal hydroxide + hydrogen
What is the chemical formula of calcium hydroxide?
Ca(OH)2
When group 2 elements burn in oxygen, what is the only product formed?
Solid white oxides
What is the chemical formula of calcium oxide??
CO
When group 2 elements react with chlorine, what do they form?
Chlorides
What is the chemical formula of calcium chloride?
CaCl2
Why are metal hydroxides strongly alkaline?
Because of the OH- ions
Are the oxides of he group 2 elements soluble?
Yes, and it increases as you go down group 2
Why do the group 2 oxides form more strongly alkaline solutions as you go down the group?
Because the hydroxides get more soluble
As they are bases, what are the oxides and hydroxides of group 2 metals able to do?
Neutralise dilute acids, and form salts
When metal hydroxides react with water, what do they form?
Metal hydroxides
When metal oxides react with dilute HCl, what do they form?
Metal chlorides and water
When metal hydroxides react with HCl, what do they form?
Metal chlorides and water
What happens to the solubility of group 2 hydroxides as you go down the group?
The solubility increases
What is a sulfate ion?
SO4 2-
What happens to the solubility of group 2 sulfates as you go down the group?
The solubility decreases
What is thermal decomposition?
When a substance breaks down (decomposes) when heated.
What is the relationship between how thermally stable a compound is and how much heat is required to break it down?
The more thermally stable a compound is, the more heat is required to break it down
What are anions?
Negative ions
What happens to large negative ions when in the presence of a cation?
They can be made unstable, distorting the anion
What is the relationship between the amount of distortion and the stability of the compound?
The greater the distortion, the less stable the compound
Why do large cations cause less distortion than small cations?
Because large cations have lower charge density
Why do carbonate/nitrate compounds become more stable as you go down the group?
Because the larger the cation, the lower the charge density, so the less distortion
What is a carbonate ion?
CO3 2-
What is a nitrate ion?
NO3 2-
Are group 1 carbonates thermally stable?
Yes, you can’t decompose them with a bunsen burner
What do group 1 nitrates decompose to form?
The metal nitrite and oxygen
What is the chemical formula of magnesium nitrite?
MNO2
What do group 2 carbonates decompose to form?
Metal oxides and carbon dioxide
What do group 2 nitrates decompose to form?
Metal oxide, nitrogen dioxide, and oxygen
How do you test the thermal stability of nitrates?
- How long it takes for an amount of oxygen to be produced
- How long it takes for NO2 to be produced (brown gas)
How do you test the thermal stability of carbonates?
-How long it takes for carbon dioxide to be produced
What is the flame colour of lithium?
Red
What is the flame colour of sodium?
Orange/yellow
What is the flame colour of potassium?
Lilac
What is the flame colour of rubidum?
Red
What is the flame colour of caesium?
Blue
What is the flame colour of calcium?
Brick-red
What is the flame colour of strontium?
Crimson
What is the flame colour of barium?
Green
How do you do a flame test?
- Mix with HCl
- Heat with a piece of platinum or nichrome wire
What happens to the electronegativity values as you go up group 2?
They increase
What colour is bromine in water?
Yellow/orange
What colour is iodine in water?
Brown
What colour is bromine in hexane?
Orange/red
What colour is iodine in hexane?
Pink/violet
What happens to the reactivity of halogens as you go down the group?
They decrease in reactivity
Why do halogens decrease in reactivity as you go down the group?
- They react by gaining an electron
- Their radius and number of shells gets bigger as you go down the group, so it is harder for larger atoms to attract an electron
What happens to the melting and boiling points of halogens as you go down the group?
Increase as the London forces between the molecules get stronger as you go down the group
If bromide is displaced and bromine is formed, what colour will the mixture turn?
Orange
If iodide is displaced and iodine is formed, what colour will the mixture turn?
Brown
When halogens react with group 1 and 2 metals, what is produced?
A salt, e.g. LiF and MgCl2
How do you make bleach?
2NaOH + Cl2 —> NaClO +NaCl +H20
When you mix chlorine with water, what is produced?
A hypochlorous acid HClO
What does Hypochlorous acid ionise to make?
Chlorate ions which kill bacteria
What happens to the reducing power of halides as you go down the group?
The reducing power increases as it is easier for them to lose their outer electron
When a potassium halide reacts with sulfuric acid, what is produced?
Hydrohalide + KHSO4
What happens when KBr reacts with sulfuric acid?
KHSO4 + HBr
What happens when potassium iodide reacts with sulfuric acid?
KHSO4 + hydrogen iodide
What is KHSO4?
Potassium bisulfate
What are the main properties of hydrogen halides?
- Acidic gases
- Can dissolve in water to produce misty fumes of acidic gases
How do you test for halides?
- Add dilute nitric acid to remove ions that interfere with the reaction
- Add silver nitrate solution and a precipitate of the silver halide is formed
What colour is the precipitate of AgCl?
White
What colour is the precipitate of AgBr?
Cream precipitate
What colour is the precipitate of AgI?
Yellow
What happens when AgCl is added to ammonia?
A colourless solution is formed
What happens when AgBr is added to ammonia?
Dissolves in concentrated ammonia to give a colourless solution
What happens when AgI is added to ammonia?
Precipitate does not dissolve
How do you test for carbonates?
-With dilute hydrochloric acid, carbonates will fizz because they give off carbon dioxide
How do you test for carbon dioxide?
Calcium dioxide turns limewater cloudy
How do you test for sulfates?
- Add dilute HCl followed by barium chloride solution.
- If a white precipitate of barium sulfate is formed, the original compound contained a sulfate
How do you test for ammonium compounds?
It turns red litmus paper blue
Add sodium hydroxide to the substance X and gently heat the mixture. If ammonia is given off there is ammonia present
