Period 3 elements Flashcards by Farhanah Begum

PERIOD 3 - Trends in Period 3

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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

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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

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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

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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

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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.

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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

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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

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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

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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

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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.

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REACTIONS OF PERIOD 3 WITH WATER

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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

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Write an equation to show this reaction?

2Na (s) + 2H2O (l) –> 2Na+ (aq) + 2OH- (aq) + H2 (g)

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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)

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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?

1. Metal oxides have ionic bonding and for BASIC oxides (Na2O and MgO), Basic metal oxides react with Acids 2. 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.

1. Na2O + H2O ---> 2Na+ (aq) + 2OH- (aq) pH = 13/14 2. MgO + H2O --> Mg(OH)2 (s) pH = 9/10 3. Al2O3 + H2O ---> insoluble pH= 7 4. SiO2 + H2O --> Insoluble pH = 7 5. P4O10 + 6H2O --> 4H3PO4 pH = 0 6. SO2 + H2O ⇌ H+ + HSO3- pH = 3 7. SO3 + H2O --> 2H+ + SO42- pH = 0/1

PERIOD 3 OXIDES WITH ACIDS AND ALKALIS

What acids do metal oxides react wiht?

1. Na2O reacts with HCL 2. 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

1. Na2O (s) + 2HCl (aq) --> 2NaCl (aq) + H2O (l) 2. 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)

1. SiO2 (s) + 2NaOH (aq) ---> Na2SiO3 (aq) + H2O (l) 2. P4O10 (S) + 12NaOH (aq) ---> 4Na3PO4 (aq) + 6H20 (l) 3. SO2 + 2NaOH (aq) ---> Na2SO3 (aq) + H2O (l) 4. SO3 + 2NaOH (aq) ---> Na2SO4 (aq) + H2O (l)

DONE!