Period 3 elements Flashcards
PERIOD 3 - Trends in Period 3
What is Periodicity?
Periodicity is a pattern, in chemical or physical properties across a row of elements (a period) which repeat across the next row of elements
Describe the trend as we go across period 3?
- Atomic radii decreases
- Due to increasing nuclear charge
- (more protons) and there is similar shielding
- Therefore the nucleus attracts the outer electrons more strongly
Describe Trend in Electronegativity as we go across period 3?
- Electronegativity increases as we go across a period
- Due to increasing nuclear charge
- And there is similar shielding
- Therefore more able to withdraw electron density from a covalent bond
Describe trend in First Ionisation energy for period 3?
Generally across a period
- There is increasing nuclear charge
- And there is similar shielding
- Therefore the outer electron is attracted more strongly to the nucleus
What are some exceptions when it comes to period 3 elements first ionisation energy?
- 1st I.E of Al is less than Mg as Al’s Outer electron is in a higher 3p Orbital, Whereas Mg’s outer electron is in a 3s orbital
- 1st 1.E of S is less than P’s , as S has a pair of electrons in the same 3P orbital which repel.
Which Period 3 metals undergo metallic bonding?
Describe their their melting and boiling points?
- Na, Mg, Al - Metal Lattices
- Metallic bonding is the attraction between positively charged ions and delocalised outer shells electrons
- m.p and b.p increases from Na<Mg<Al
- Due to stronger metallic bonding
- Smaller ionic radii
- More delocalised electrons
What element in Period 3 has the highest melting and boiling point?
- Silicon has the highest melting point
- As it has strong covalent bonds between all atoms
- Macromolecular lattice
- Lots of energy is required to break the bonds
Which elements from period 3 have low melting points?
- Phosphorus, Sulphur and Chlorine have low melting points
- Due to weak Van Der Waals Forces
- Between covalent molecules
Why is the melting and boiling point of sulphur greater than Phosphorus?
- Sulphur has a larger molecule
- Which are more polarisable
- Has stronger Van Der Waals Forces Between Its Molecules
What element in Period 3 Has the lowest Melting and boiling Point?
Argon - Has the lowest melting and boiling point
- Made up of single atoms - Monotomic
- Has weakest Van Der Waals forces between it’s atoms.
REACTIONS OF PERIOD 3 WITH WATER
Describe the reaction between Sodium metal and Cold water?
What observations could be seen?
Reacts very vigorously with cold water
- Sodium reacts very vigorously
- sodium floats
- Bubbles/Fizzes vigorously
- Colourless solution is formed
- Solution is strongly alkaline (pH = 13/14) when a universal indicator is added
Write an equation to show this reaction?
2Na (s) + 2H2O (l) –> 2Na+ (aq) + 2OH- (aq) + H2 (g)
Describe the reaction between magnesium and steam, state the observations that would be seen?
- Magnesium reacts with stea to form magnesium oxide and hydrogen gas
- White solid is formed
- Magnesium glows orange as it reacts
- gas is given off (H2)
Draw an equation to show this reaction?
Describe the reaction when magnesium reacts with cold water?
Draw an equation to show this reaction?
PERIOD 3 ELEMENTS AND OXYGEN
Describe the reaction between the following period 3 elements and oxygen, what colour flame is produced:
1. Sodium
2. Magnesium
3. Aluminium
4. Silicon
5. Phosphorous
6. Sulphur
- reacts vigorously with oxygen and Yellow flame
- Magnesium reacts vigorously with oxygen and a white flame is produced
- Aluminium reacts slowly in oxygen and produces a white flame
- Silicon reacts very slowly to produce a white flame
- Phosphorous spontaneously combusts with oxygen and a white flame is produced
- Sulphur burns steadily in oxygena dn a blue flame is produced
What products do period 3 elements form when reacted with oxygen?
They all form Metal oxides - and white solids except Sulphur
Write equations for each of the following period 3 elements with oxygen:
1. sodium
2. Magnesium
3. Aluminium
4. Silicon
5. Phosphorus
6. Sulphur
- 4Na + O2 –> 2Na2O
- 2Mg + O2 —-> 2MgO
- 2Al + 3/2 O2 —> Al2O3
- Si+ O2 –> SiO2
- P4 + 5o2 –> P4O10
- S + O2 —> SO2 ( Misty fumes, choking smell, colourless gas)
REACTIONS OF PERIOD 3 OXIDES
What can the trend in melting point of period 3 oxides be explained by? DRAW A GRAPH TO SHOW TREND!
The trend in meting point across the period can be explained by the structure and bonding of period 3 oxides
What type of bonding occurs between sodium oxide and magnesium oxide? What structure is formed?
Ion bonding and an ionic lattice is formed
Why do these structures have a high melting point?
High melting point is due to strong electrostatic forces of attraction between oppositely charged ions. MgO has a higher m.p than Na2O as Mg2+ ions have a greater charge/more protons and a smaller ionic radii
What bonding occurs in aluminium oxide?
Al2O3 (s) - forms an ionic bond with a covalent character, and has an ionic lattice
Why does Aluminium form an ionic bonds with a covalent character?
O2- ions are non-spherical as have been polarised by Al3+ ions, as Al3+ have high charge/size ration. High m.p as strong electrostatic forces of attraction between Al3+ and O2-
Describe bonding and structure when Silicon, Phosphorus and Sulphur react with oxygen? And state why they either has a low or high melting point?
- SIO2 - Forms a macromolecular - covalent structure -= therefore has a high melting point as lot’s of energy is required to break strong covalent bonds
- P4O10 and SO2 are simple molecular covalent substances - therefore little energy is required to break weak intermolecular forces between molecules
- P4O10 > SO2 as P4O10 is a larger molecule, so more polarisable, stronger van Der Waals forces
PERIOD 3 OXIDES WITH WATER
What type of oxides do metal oxides and Non-metal oxides form? And what does each of these particular oxides react with?
- Metal oxides have ionic bonding and for BASIC oxides (Na2O and MgO), Basic metal oxides react with Acids
- Non-metal oxides have covalent bonding and for ACIDIC oxides (P4O10, SO2, SIO2) , Acidic non-metal oxides react with bases
(so across the period table, bonding goes from ionic to covalent and oxides turn from basic to acidic)
Describe what is formed when Period 3 Oxides react with water. Write equations to show these reactions. And Give the approximate pH for the resulting solution.
- Na2O + H2O —> 2Na+ (aq) + 2OH- (aq) pH = 13/14
- MgO + H2O –> Mg(OH)2 (s) pH = 9/10
- Al2O3 + H2O —> insoluble pH= 7
- SiO2 + H2O –> Insoluble pH = 7
- P4O10 + 6H2O –> 4H3PO4 pH = 0
- SO2 + H2O ⇌ H+ + HSO3- pH = 3
- SO3 + H2O –> 2H+ + SO42- pH = 0/1
PERIOD 3 OXIDES WITH ACIDS AND ALKALIS
What acids do metal oxides react wiht?
- Na2O reacts with HCL
- MgO reacts with sulphuric acid
What alkali’s do non-metal oxides react with?
All non-metal oxides react with Sodium hydroxide (NaOH)
Draw equations to show the reaction of Period 3 metal oxides with Acids
- Na2O (s) + 2HCl (aq) –> 2NaCl (aq) + H2O (l)
- MgO (s) + H2SO4 (aq) –> MgSO4 (aq) + H2O (l)
Write equations to show how non-metal period 3 oxides react with an alkali (such as NaOH)
- SiO2 (s) + 2NaOH (aq) —> Na2SiO3 (aq) + H2O (l)
- P4O10 (S) + 12NaOH (aq) —> 4Na3PO4 (aq) + 6H20 (l)
- SO2 + 2NaOH (aq) —> Na2SO3 (aq) + H2O (l)
- SO3 + 2NaOH (aq) —> Na2SO4 (aq) + H2O (l)
DONE!
