PERIOD 3 Flashcards
Trend in atomic radius across period 3
Increase in nuclear charge
Same amount of shielding
Outer electron stringly attracted to nucleus
Electronegativity across period 3
Increase in nuclear charge
Same shielding
Elements are increasingly capable of withdrawing elevtrkn density from a covalent bond
1st ionisation energy across period 3
Increase in nuclear charge
Same shielding
Electrons are held strongly so require more energy to be removed
Mg has a 3s electron removed
Al has a 3p electron removed
3p is higher in energy than 3s
P has a 3p electron removed which is unpaired
S has a 3p electron removed which is paired
S has a lower ionisation energy due to electron pair repulsion
Melting point and boiling point across period 3
The charge on the metal ion increases from Na+ to Al3+
- The size of the metal ion decreases across the row
- Therefor there is an increase in the strength of attraction between the
metal ions and delocalised electrons.
Silicon has the highest MP because:
- It has a macromolecular structure
- With lots of covalent bonds
- Which are very strong
For the non-metals:
- P4, S8 and Cl2 all have a simple molecular structure with Van der Waals
intermolecular forces.
- Strength of the Van der Waals depends on the size of the molecule and
S8 is largest, followed by P4 then Cl2.
- Argon exists as single atoms with the weakest Van der Waals out of all of
them.
Aluminium has the highest boiling point because:
- Once silicon has been melted most of its strong covalent bonds have
been broken, so boiling it requires only a little extra energy.
- In the liquid state Aluminium still has strong electrostatic attraction between ions and delocalised electrons, and so still requires a large
amount of energy to boil.
How do the acid/base properties of the P3 oxides change going across
the period?
Across the period the oxides change from being basic to neutral to acidic
What is the relationship between the bonding and acid/base properties of the period 3 oxides?
- The oxides which are IONICALLY bonded tend to be ALKALINE
- The oxides which are COVALENTLY bonded tend to be ACIDIC
Why does MgO have the highest melting point of all the P3 oxides?
MgO has ionic bonds.
There are strong electrostatic forces of attraction between oppositely charged ions.
These require a lot of energy to overcome.
Why does Al2O3 have more covalent character then MgO
The Al3+ ion is smaller than the Mg2+ ion.
- This means the Al3+ ion is more polarising than the Mg2+ ion.
- This distorts the electron cloud around the O2- ion more so that there is
more electron density shared between the two ions.
For the oxides of Phosphorus and Sulfur, why does P4O10 have the
highest melting point, followed by SO3 then SO2.
These all have simple molecular structures.
- They all have Van der Waals intermolecular forces between molecules.
- P4O10 is the largest molecule so has the strongest VdW, whereas SO2 is
the smallest so has the weakest VdW.
Why does SiO2 have a high melting point?
This has a macromolecular/giant covalent structure.
- It has lots of covalent bonds.
- Which are very strong.
Reaction of the period 3 elements with water
1.Sodium
2.Magneisum
3.Chlorine
1.
2Na(s) + 2H2O(l)→2NaOH(aq) + H2(g)
2.
Mg(s) + 2H2O(l)→Mg(OH)2(aq) + H2(g)
Reaction with steam
Mg(s) + H2O(g)→MgO(s) + H2(g)
3.
Cl2(g) + H2O(l) HClO(aq) + HCl(aq)
In presence of bright sunlight
2Cl2(g) + 2H2O(l) → 4HCl(aq) + O2(g)
Reaction of period 3 elements with oxygen
1. Sodium
2. Magnesium
3. Aluminium
4.silicon
5. Phosphorus
6.sulfur
Equations and observations
- -For simple oxide
2Na(s) + 1⁄2O2(g)→Na2O(s)
-For peroxide
2Na(s) + O2(g)→Na2O2(s)
Orange flame to white solid - 2Mg(s) + O2(g) → 2MgO(s)
Bright ahite flame to white solid
3.
4Al(s) + 3O2(g) → 2Al2O3(s)
White flame to white solid
4.
Si(s) + O2(g) → SiO2(s)
Oragne foame to white solid
5.
P4(s) + 5O2(g) → P4O10(s)
Whire flame to no white fumes produced
6.
S(s) + O2(g)→SO2(s)
Pale boue flame to colourless gas
Reactant of the period 3 oxide with water
1. Na2O
2. MgO
3. P4O10
4.SO2
5. SO3
- Na2O(S) + H2O(I) —-> 2Na+ (AQ) + 2OH-(AQ)
- MgO(s) + H2O(I)—->Mg(OH)2(AQ)
3.
P4O10(s) + 6H2O(I) —-> 4H3PO4(aq)
4.
SO2(G) +H2O(I) —-> H2SO3(AQ)
5.
SO3(g) + H2O(I) —->H2SO4(AQ)
Basic oxides equations
Na2O +H2SO4 —-> Na2SO4 +H2O
MgO + 2HCl —-> MgCl2 +H2O
What does anlopetric mean
Species that can act as acid or a base
