Periodicity and Redox (CDS) Flashcards
(55 cards)
What happens to the atomic radius as you go down a group and why?
Increases due to extra shell of electrons
What happens to the atomic radius as you go across a period and why?
Decreases due to increased nuclear charge with the same shell and the same shielding
What happens to the 1st ionisation energy as you go down a group and why?
Decreases as force of attraction between outer electron and nucleus is weaker due to increased shielding so it’s easier to remove
What happens to the 1st ionisation energy as you go across a period and why?
General increase due to increased nuclear charge and decreased atomic radius with the same shell and the same shielding
In period 3, why does:
1. Mg have a higher 1st I.E. than Al
2. P have a higher 1st I.E. that S
- Outer electron goes from s to p orbital so it’s easier to remove
- Outer configuration goes from p3 to p4 so electron pair repulsion makes electron easier to remove
What type of structure is Silicon?
Giant covalent/Macromolecular
What type of structure does Na, Mg and Al have?
Giant metal lattice
What type of structure does P, S and Cl have?
Molecular/Simple covalent
What type of structure is Argon?
Atomic
Which element in period 3 has the highest melting point and why?
Silicon due to the many string covalent bonds in its structure which take lots of energy to break
Why do melting points increase going across from Na to Al?
Charge on the metal ions gets larger, so ions are smaller and have a higher charge density so metallic bonding is stronger as there are more electrons. Electrostatic forces take more energy to overcome.
Explain the trend in melting points between P, S Cl and Ar
Melting points of simple molecular structures depends on the size of the VdW forces, which depends on the number of the electrons and how closely the molecules can pack together. As a result, melting points go S8 > P4 > Cl2 > Ar
Explain the trend in melting points in group 2
Melting points are high due to the strong metallic structure. Starting at calcium, melting points decrease down the group due to the increased atomic radius which results in weaker metallic bonding as the force of attraction between the nucleus and the electrons in the lattice is weaker. Mg does not follow this pattern; it has the lowest melting point.
What happens to the reactivity of group 2 elements as you go dow the group?
Increases
Oxidation state of group 2 metals:
0 to +2
What is magnesium hydroxide used for?
Used in indigestion remedies to neutralise excess stomach acid which can cause heartburn.
Reaction of magnesium with cold water vs steam
Magnesium reacts very slowly with cold water but reacts quickly with steam
General equation for the reaction of group 2 metals with water
M + H2O –> M(OH)2 + H2
Reaction of Mg with steam:
Mg + H2O –> MgO + H2
What is calcium hydroxide used for?
To neutralise acidic soil
What happens to the solubility of group 2 hydroxide precipitates down the group
Increases
What happens to the solubility of group 2 sulphate precipitates down the group
decreases
Uses of barium sulphate
Used in barium meal as a digestive tracer as it is insoluble and won’t enter the blood stream where it would be toxic. Acidified barium chloride is added to the solution and is sulfate ions are present, then a white insoluble precipitate of barium sulfate is formed.
Uses of acidified barium chloride
Acidified Barium chloride is a reagent used to test for sulfate ions and carbonate ions. They both form white precipitates.
Acidified Barium chloride can also remove carbonate ions from a sample to prevent a false positive result
