Chapter 9. The Periodic Table: Chemical Periodicity Flashcards
Note
Know where the alkali metals, alkaline earth metals, transition metals, metaloids, halogens, noble gases and lanthanides and actinides are located on the periodic table.
Note
Know where the different s,p,d,f blocks are located on the periodic table
Why are scandium and zinc not transition metals?
They do not form any compounds in which they have partly filled d-orbitals.
What is the reactivity periodicity of elements?
For metals, they tend to get more reactive down a group but non-metals tend to get more reactive up a group.
Note
In period 3:
-Na , Mg and Al are metals with giant metallic structures, forming ionic compounds
-Silicon forms covalent bonds(4), giant covalent(giant molecular crystal)
-Phosphorus, sulfur and chlorine are non-metals, molecular, P4 S8 Cl2
-Argon is a noble gas, atomic
-Atomic radius decreases acroos the period as nuclear charge increases
-Ionic radius decreases but metal ions are smaller than no-metal ions beacuse non-metals gain a shell while metals lose one, Silicon does not form ions
-Giant structures tend to have higher melting points, hence general increase in melting point up to silicon., as ionic charge increases melting point increases as more electrons join the sea of delocalised electrons
-For non-metals, S > P > Cl as melting point depends on vanderWaals forces, which depends on the number of electrons in the molecule and how closely the molecules can pack together.
-Reactivity of metals decrease across the period as the number of electrons that have to be lost to form an ion increases
-Reactivity of non-metls increases across the period as the number of electrons that have to gained to form an ion decreases
Note
-Na, Mg react with cold water, Cl reacts with water
-2Na + 2H2O –> 2NaOH + H2 (13-14 pH)
-Mg + 2H2O –> Mg(Oh)2 + H2
-Mg + H2O –> MgO + H2 (hot magnesium and steam)
Note
-Reactions with oxygen
-2Na + 0.5O2 –> Na2O (yellow flame and white sodium oxide(might have yellowish appearance due to Na2O2 - Sodium peroxide))
-2Mg + O2 –> 2MgO (bright white flame, white MgO
-4Al + 3O2 –> 2Al2O3 (burns brightly, white aluminium oxide, Al is reactive but forms a layer which prevents further reaction
-Si + O2 –> SiO2
-4P + 5O2 –> P4O10 (red Phosphorus needs to be heated first but white does not(allotropes) white smoke of Phosphorus pentoxide, sometimes P2O3 is formed when oxygen is limited)
-S + O2 –> SO2 (burns with a blue flame, colourless sulfur dioxide, a little sulfure trioxide)
Note
-Reactions with chlorine gas
-Na and Mg vigorously when heated and plunged into chlorine gas, white fumes of the ionic chloride
-2Na + Cl2 –> 2NaCl
-Mg + Cl2 –> MgCl
-4Al + 6Cl2 –> 2Al2Cl6
-With non-metals simple molecules arew formed
-Si + 6Cl2 –> SiCl4
-2P + 3Cl2 –> 2PCl3 and 2P + 5Cl2 –> 2PCl5
-S + Cl2 –> SCl2 or SCl4 or S2Cl2
Amphoteric Oxides
Can behave as both an acid or a base
-Al2O3 + 6HCl –> 2AlCl3 + 3H2O
-Al2O3 + 2NaOH + 3H2O –> 2NaAl(OH)4 - Sodium Aluminate
Note
Aluminium oxide and Silicon dioxide are insoluble in water
Note
-P4O10 + 6H2O –> 4H3PO4 1-2 pH
-SO2 + H2O –> H2SO3 2-3 pH
-SO3 + H2O –> H2SO4 0-1 pH
Note
The ionic chlorides dissoleve in water to form ionic solutions, the non-metal chloridesreact with water to form acidic solutions containing H+ and Cl- ions
-AlCl3 + 3H2O –> Al(OH)3 + 3H+ + 3Cl-
-SiCl4 + 2H2O –> SiO2 + 4H+ + 4Cl-
-PCl5 + 4H2O –> H3PO4 + 5H+ + 5Cl-
-magnesium chloride hydrolyses to a small extent so the pH of the resulting solution is slightly acidic otherwise ionic solutions are neutral
-For aluminium its 2-3
-For the rest its 1
-For Sulfur its ~1
What is an alotrope?
A different form of the same element with a different arrangement of atoms
Note
For molecular structures, when they melt, their covalent bonds remain intact but the van der Waals forces break, so melting point depends on these.
Na2O
Solid gas solid, yellow orange flame, fast
