Topic 4- Inorganic chemistry and the periodic table Flashcards
(28 cards)
What are group 2 elements?
Group 2 are metals that form 2+ ions when they react. All group 2 metals have electron configurations that end s 2
Trends of Group 2 elements
The atomic radius increases when you go down group 2. This means the first ionisation energy decreases when we go down group 2 because there is more shielding meaning weaker attraction between the nucleus and outer electrons.
This makes it easier to remove the outer electron and so less energy is required
What happens when group 2 elements react with water?
Group 2 elements react with water to form bases. The reaction with water to form metal hydroxides. The reactivity increases with water when you go down. When magnesium reacts with steam more vigorously and forms magnesium oxide instead of hydroxide
What happens when group 2 elements react with oxygen?
Group 2 elements react with oxygen to form a base. The reaction with oxygen to form metal oxides. Group 2 oxides are white solids
What happens when group 2 elements react with chlorine?
Group 2 elements react with chlorine to form chlorides. Reaction with chlorine to form metal chlorides.
What happens when group 2 oxide react with water?
Group 2 oxides form bases when reacted with water. Alkaline solutions formed when added to water
What is the trend in solubility of group 2 hydroxides?
They become more strongly alkaline as you go down the group as the hydroxides become more soluble
What is the trend in solubility of group 2 sulfates?
Group 2 sulfates solubility decreases when you go down the group
What is the test for carbon dioxide?
Lime water turns cloudy as white precipitate form when carbon dioxide is present
What is the test for hydrogen?
Hydrogen ignites in the air. If hydrogen I present in a test tub a lighted splint creates a squeaky pop
What is the test for oxygen?
A glowing splint will re-ignite in the presence of oxygen
What is thermal stability?
Thermal stability is a measure of the extent to which a compound decomposes when heated
What happens when a Group 2 carbonate thermally decomposes?
The carbonate breaks down into metal oxides and carbon dioxide
What happens when a group 2 nitrate thermally decomposes?
The nitrate breaks down into metal oxides, nitrogen dioxide and oxygen if brown fumes are observed. If not the nitrate breaks down into metal nitrate and oxygen
What are the trends in thermal stability?
Carbonates and nitrates become more thermally stable as you go down group 2
Why do carbonates and nitrates become more thermally stable as we go down group 2?
Near the top of group 2 elements have a high charge density which means the charge is less spread over an area. This distorts the electron cloud of the nitrate and carbonate so it is less stable. When you go down the group there is a low charge density so it is more thermally stable
What are the trends in thermal decomposition in group 1 carbonates?
Group 1 carbonates thermally decompose and are more thermally stable than group 2 compounds. Except for lithium carbonate which has a high charge density which distorts the electron cloud making it less stable
What are the trends in thermal decomposition in group 1 nitrates?
Group 1 nitrates break down into nitrites and oxygen. Except for lithium nitrate which decomposes to form lithium oxide, nitrogen dioxide and oxygen
How do you conduct the flame test?
- Dip nichrome wire in concentrated HCL
- Dip into the sample
- Hold the end of the wire in the flame and observe the colour
What is the flame test?
The flame test is a chemical test that identifies the presence of a cation in a compound
Flame test colours
Lithium- red Sodium- yellow Potassium- lilac Rubidium- red/purple Caesium- violet Beryllium- no colour Magnesium- no colour Calcium- red Strontium- red Barium- green
What cause the colour in the flame test?
When electrons absorb energy they get excited and move to a higher energy level. This movement is immediately followed by the electrons moving to a lower energy level (ground state) which releases energy. This energy corresponds to the radiation in the visible light spectrum hence a colour is seen.
What is the test for ammonium ions?
Ammonium ions is added to sodium hydroxide to form ammonia which has pungent smell but it turns damp red litmus paper blue
Halide displacement reactions?
- chlorine displaces bromine and iodine
- bromine displaces iodine but not chlorine
- iodine doesn’t displace either chlorine or bromine
