Period 3 Elements: Properties and Reactivity Overview
Explore the properties and reactivity trends of Period 3 elements, including reactions with water, oxygen, and more. Understand electron configurations, ionization energy trends, and bonding characteristics. Dive into the behavior of sodium, magnesium, and other elements to grasp their interaction with different substances.
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PROPERTIES OF PERIOD 3 ELEMENTS Learning Objectives: 1. Identify the products of the reactions of sodium and magnesium with water. 2. Describe the trends in the reactivity of period 3 elements with oxygen and of their products with water, acids and bases in relation to the types of bonding present. 3. Explain trends in the melting points of period 3 oxides in terms of structure and bonding. Specification Reference: 3.2.4
ELECTRONIC CONFIGURATION - RECAP The Aufbau principle states that ELECTRONS ENTER THE LOWEST AVAILABLE ENERGY LEVEL . In period 3 the electrons fill the 3s orbital first, followed by the 3p orbitals. Notice how the electrons in the 3p orbitals remain unpaired, if possible, according to Hund s Rule. 1s 2s 2p 3s 3p Na 1s2 2s2 2p6 3s1 Mg 1s2 2s2 2p6 3s2 Al 1s2 2s2 2p6 3s2 3p1 Si 1s2 2s2 2p6 3s2 3p2 P 1s2 2s2 2p6 3s2 3p3 S 1s2 2s2 2p6 3s2 3p4 Cl 1s2 2s2 2p6 3s2 3p5 Ar 1s2 2s2 2p6 3s2 3p6
FIRST IONISATION ENERGY - RECAP TREND Theoretically, the value should increase steadily across the period due to the increased nuclear charge. HOWEVER... There is a DROP in the value for aluminium because the extra electron has gone into a 3p orbital. The increased shielding makes the electron easier to remove. 1500 1000 There is a DROP in the value for sulphur. The extra electron has paired up with one of the electrons already in one of the 3p orbitals. The repulsive force between the electrons means that less energy is required to remove one of them. 3s 3p 500 3s 3p Na Mg Al Si P S Cl Ar
METALS OF PERIOD 3 REACTION WITH WATER Sodium vigorous reaction hydrogen evolved strong alkaline solution produced (pH = 14) Na(s) + 2H2O(l) > 2NaOH(aq) + H2(g) Magnesium slow reaction with cold water weaker alkaline solution produced (pH 9-11) Mg(s) + 2H2O(l) > Mg(OH)2(aq) + H2(g) very fast reaction with steam Mg(s) + H2O(l) > MgO(S) + H2(g) LO1: Identify the products of the reactions of sodium and magnesium with water.
METALS OF PERIOD 3 REACTION WITH OXYGEN Na2O MgO Al2O3 SO2 Melting point / K 1548 3125 2345 200 bonding structure classification ionic ionic ionic/cov covalent giant lattice lattice giant giant lattice simple molecule basic basic amphoteric acidic solubility in water solution pH very sparingly insoluble reacts 14 9 3 LO2: Describe the trends in the reactivity of period 3 elements with oxygen and of their products with water, acids and bases in relation to the types of bonding present.
OXIDES OF PERIOD 3 ELEMENTS PREPARATION metals produce basic oxides non-metals produce acidic oxides aluminium oxide is an amphoteric oxide (acidic and basic properties) ionic oxides have high melting points ionic oxides conduct electricity when molten most oxides can be prepared by direct combination (EXC. SO3) 0 0 +2 -2 2Mg(s) + O2(g) > 2MgO(s) 0 0 +3 -2 4Al(s) + 3O2(g) > 2Al2O3(s) 0 0 +4 -2 S(s) + O2(g) > SO2(g) LO2: Describe the trends in the reactivity of period 3 elements with oxygen and of their products with water, acids and bases in relation to the types of bonding present.
OXIDES OF PERIOD 3 ELEMENTS PROPERTIES Na2O white solid giant ionic lattice soluble in water to form a strongly alkaline solution (pH = 13-14) Na2O(s) + H2O(l) > 2NaOH(aq) reacts with acids to form salts A BASIC OXIDE Na2O(s) + HCl(aq) > NaCl(aq) + H2O(l) Na+ Na+ 2- O LO2: Describe the trends in the reactivity of period 3 elements with oxygen and of their products with water, acids and bases in relation to the types of bonding present.
OXIDES OF PERIOD 3 ELEMENTS PROPERTIES MgO white solid giant ionic lattice sparingly soluble in water to form hydroxide (pH = 9) (Low solubility is due to metal s greater charge density) MgO(s) + H2O(l) > Mg(OH)2(aq) reacts with acids to form salts A BASIC OXIDE MgO(s) + 2HCl(aq) > MgCl2(aq) + H2O(l) 2- 2+ O Mg LO2: Describe the trends in the reactivity of period 3 elements with oxygen and of their products with water, acids and bases in relation to the types of bonding present.
OXIDES OF PERIOD 3 ELEMENTS PROPERTIES Al2O3 giant lattice with some covalent character insoluble in water AMPHOTERIC; it reacts with both acids and alkalis to give salts with acids Al2O3(s) + 6HCl(aq) > 2AlCl3(aq) + 3H2O(l) with alkalis Al2O3(s) + 2NaOH(aq) + 3H2O(l) > 2NaAl(OH)4(aq) LO2: Describe the trends in the reactivity of period 3 elements with oxygen and of their products with water, acids and bases in relation to the types of bonding present.
OXIDES OF PERIOD 3 ELEMENTS PROPERTIES SO2 simple covalent molecule O O S ANGULAR / BENT soluble in water reacts with water to give a weak acidic solution (pH = 3) SO2(g) + H2O(l) 2H+(aq) + SO32-(aq) converted to sulphur trioxide in the CONTACT PROCESS LO2: Describe the trends in the reactivity of period 3 elements with oxygen and of their products with water, acids and bases in relation to the types of bonding present.
OXIDES OF PERIOD 3 ELEMENTS PROPERTIES SO3 simple covalent molecule O O S TRIGONAL PLANAR O reacts violently with water to give a strong acidic solution (pH = 0) SO3(g) + H2O(l) >2H+(aq) + SO42-(aq) LO2: Describe the trends in the reactivity of period 3 elements with oxygen and of their products with water, acids and bases in relation to the types of bonding present.
OXIDES OF PERIOD 3 REACTION WITH WATER Ionic oxides of metals Na and Mg both contain oxide ions (O2-). When they dissolve in water, the O2- ions accept protons from the water molecules forming hydroxide ions. The solutions are both alkaline however, NaOH is more soluble so has the higher pH compared to Mg(OH)2. Na2O(s) + H2O(l) > 2NaOH(aq) MgO(s) + H2O(l) > Mg(OH)2(aq) pH 12-14 pH 9-10 The reactions of some of the simple covalent oxides are shown below: LO2: Describe the trends in the reactivity of period 3 elements with oxygen and of their products with water, acids and bases in relation to the types of bonding present.
OXIDES OF PERIOD 3 REACTIONS WITH ACIDS AND BASES The equation for neutralising an acid and base is: Sodium and Magnesium oxides are basic so will neutralise acids: Na2O(s) + 2HCl(aq) > 2NaCl + H2O(l) MgO(s) + H2SO4(aq) > MgSO4(aq) + H2O(l) Silicon, Phosphorous and Sulphur oxides are basic so will neutralise bases: SiO2(s) + 2NaOH(aq) > Na2SiO3(aq) + H2O(l) P4O10(s) + 12NaOH(aq) > 4Na3PO4(aq) + 6H2O(l) SO2(g) + 2NaOH(aq) > Na2SO3(aq) + H2O(l) SO3(g) + 2NaOH(aq) > Na2SO4(aq) + H2O(l) Aluminium oxides are amphoteric so will neutralise acids or bases: Al2O3(s) + 3H2SO4(aq) > Al2(SO4)3(aq) + 3H2O(l) Al2O3(s) + 2NaOH(aq) > 3H2O(l) + 2NaAl(OH)4(aq) LO2: Describe the trends in the reactivity of period 3 elements with oxygen and of their products with water, acids and bases in relation to the types of bonding present.
OXIDES OF PERIOD 3 ELEMENTS MELTING POINTS The differences in melting points of the period 3 oxides are due to differences in structure and bonding: Metal oxides all have high melting points because they form giant ionic lattices. MgO has a higher melting point than Na2O due to the Mg2+ ion attracting the O2- more strongly than Na+. However the Al2O3 is lower than expected due to the partial covalent character of Al3+. SiO2 is higher than expected due to it having a giant macromolecular structure. P4O10 and SO3 have lower melting points due to their simple molecular structures which have only weak intermolecular forces. LO3: Explain trends in the melting points of period 3 oxides in terms of structure and bonding.
