Inorganic Chemistry and the Periodic Table Flashcards
Trends in atomic radius for group 2 elements
Group 2 elements form 2+ ions when they react
Atomic radius increases down the Group.
As one goes down the group, the atoms have more shells of electrons making the atom bigger.
What is a common name given to group 2 metals?
Alkaline earth metals
What is the most reactive metal of group 2?
Barium
List 3 physical properties of group 2 metals
● High melting and boiling points
● Low density metals
● Form colourless (white) compounds
The highest energy electrons of group 2 metals are in which subshell?
S subshell
Does reactivity increase or decrease down group 2? Why?
● Increases
● Electrons are lost more easily because larger atomic radius and more shielding.
What happens to the first ionisation energy as you go down group 2? Why?
1st ionisation energy decreases as we go down group 2
Extra shells added as we go down group 2
The outer electrons are further away from the nucleus
which weakens the attraction
There is more shielding, hence the attraction between the outermost electron and the nucleus decreases
This makes it easier to remove the outer electron, so less energy is required to remove it
What type of reaction is the reaction between group 2 elements and oxygen?
Redox reaction
Write an equation for the reaction of calcium and oxygen
2Ca (s) + O2 (g) → 2CaO (s)
What is the product when group 2 elements react with water?
Hydroxide and hydrogen gas
Which group 2 element doesn’t react with water?
Beryllium
Which group 2 element reacts very slowly with water?
Magnesium
What type of reaction is the reaction between group 2 metal and water?
Redox reaction
Write an equation for the reaction of Barium and water
Ba (s) + 2H2O (l) → Ba(OH)₂ (aq) + H₂ (g)
What is oxidised and what is reduced in a reaction between group 2 metal and water?
Metal → oxidised
One hydrogen atom from each water → reduced
What are the products when group 2 oxide reacts with dilute acid?
Salt and water
Write an equation for the reaction of calcium and hydrochloric acid
CaO (s) + 2HCl (aq) → CaCl2(s) + H₂O (l)
What is formed when group 2 oxides react with water?
Metal hydroxide
Write an equation for the reaction between a group 2 oxide and water
MO (s) + H2O (l) → M(OH)2 (aq)
Which group 2 metal oxide is insoluble in water?
Beryllium oxide
Write an equation for the reaction between Mg(OH)2 and nitric acid
2HNO3 (aq) + Mg(OH)2 (aq) Mg(NO3)2 (aq) + 2H2O (l)
What is the trend in hydroxide solubility down group 2?
Increases down the group
Mg(OH)₂ is slightly soluble
Ba(OH)₂ creates a strong alkaline solution
What is the trend in sulphate solubility down group 2?
Group 2 sulphates become less soluble down the group with BaSO4 being the least soluble.
Explain the reasons for the trend of thermal stability in group 1 and 2 carbonates
Group 2 carbonates are more thermally stable as you go down the group. This is because the cations get bigger so therefore have less of a polarising effect distorting the carbonate ion less. As C-O bond is not weakened as much it harder to break down
Group 1 carbonates do not decompose except for lithium. This is because they don’t have a big enough charge density to polarise the carbonate ion as they only form 1+ ions. However Lithium ion is small enough to have a polarising effect so therefore lithium carbonate can decompose.
Explain the reasons for the trend of thermal stability in group 1 and 2 nitrates
The ease of thermal decomposition decreases down group 2 and this is because down the group the ions get larger and therefore has less charge density = less polarisation of nitrate anion and less weakening of the N―O bond.
Group 1 nitrate do not decompose with the exception of Lithium nitrate. Lithium ion is smaller enough to charge polarisation of the nitrate anion and thus weakening the N-O bond.
Flame test colours group 2
Magnesium: no flame colour (the energy emitted is outside visible spectrum)
Calcium: brick red
Strontium: red
Barium: pale green
How do you carry out a flame test?
- Use a nichrome wire
- Sterilise the wire by dipping in concentrated hydrochloric acid and then heating in Bunsen flame
- Make sure the sample powdered or grinded
- Dip wire in solid and put in Bunsen flame and observe flame
How are the colours from the flame test formed?
The heat causes the electron to get excited and thus move to a higher energy level but at this higher level the electron is unstable so then moves back down.
As it moves from a higher to lower energy level energy is emitted in the form of visible light energy which is the colour you see.
What group elements are referred to as halogens?
Group 7
List 2 properties of halogens
● Low melting and boiling points
● Exist as diatomic molecules
What is the trend in boiling point down group 7? Why?
Increases down the group because: -size of atom increases as more occupied electron shells → stronger London forces of attraction between molecules, take more energy to break
What is the trend in reactivity down group 7? Why?
Reactivity decreases because:
● Atomic radius increases
● Electron shielding increases
● Ability to gain an electron and form 1- ions decreases
Explain the trend of electronegativity down group 7
Down the group the electronegativity of the elements decreases.
This is because the atomic radii increases due to the increasing number of shells so there is reduced nuclear attraction between the outermost electron and the nucleus.
What is the trend in oxidising ability down the group? Why?
Decreases down group (Cl strongest, I weakest)
This is because Cl has the fewest occupied electron shells, greatest force of attraction between outer electrons and nucleus and thus is the easiest to gain electrons and be reduced → best oxidising agent
What is the trend in reducing ability of the halides down the group? Why?
Increases down the group (Cl- weakest, I- strongest)
This is because I- has the most occupied electron shell so outer electrons are further from the nucleus, weakest force of attraction between outer electrons and positive charge of nucleus and thus is the easiest to be oxidised and lose electrons → best reducing agent
When a more reactive halogen displaces a less reactive halide, what is the reaction called?
Displacement reaction
What is the colour of chlorine in water?
Pale green
What is the colour of bromine in water?
Orange
What is the colour of iodine in water?
Brown
What is the colour of chlorine in cyclohexane?
Pale green
What is the colour of bromine in cyclohexane?
Orange
What is the colour of iodine in cyclohexane?
Violet
Out of the 3 halides Cl-, Br- & I-, which one of these can be oxidised by chlorine?
Br- & I- ions
Write the equation for chlorine oxidising bromide ions
Cl₂ (aq) + 2Br- (aq) → 2Cl- (aq) + Br₂ (aq)
Yellow solution
Write the equation for Cl2 oxidising 2I- in cyclohexane and associated colour change
Cl₂ (aq) + 2I- (aq) → 2Cl- (aq) + I₂ (aq)
Purple solution