Join TSR
 
 About Us | FAQs | Sign in
 
HomeForumsArticlesRevision NotesPersonal StatementsUniversity GuidesHealth & RelationshipsPostgraduate StudyCareersFreshers
Join the UK's largest student community  
Advanced
Search

Join The Student Room Today

Be part of the UK's largest and fastest growing student community.

It's free to join and a lot of fun - Get inspired, express your ideas, interact and share

Join The Student Room Today

Revision:Periodicity - 13

From The Student Room

TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Chemistry > Periodicity - 13

13.1 Periodic trends Na-> Ar (the third period)

13.1.1

(This seems very much like the last bit of SL, but now with explanations)

Elements on the left are metallic...right are non-metals...Al is a metalloid (semi-metal).

Oxides : Non-metals -> Acidic oxides , Metals -> Basic oxides, Metalloids -> Amphoteric (both acidic & basic) oxides.


Oxide Na2O MgO Al2O3 SiO2
Adding H2O \mathsf{Na_2O + H_2O \longrightarrow}

\mathsf{2NaOH} 		\mathsf{MgO + H_2O \longrightarrow}

\mathsf{Mg(OH)_2} 		Insoluble Insoluble
Adding HCl \mathsf{Na_2O + H^+ \longrightarrow}

\mathsf{2Na^+ + H_2O} 		\mathsf{MgO + 2H^+ \longrightarrow}

\mathsf{Mg^{2+} + H_2O} 		\mathsf{Al_2O_3 + 6H^+ \longrightarrow}

\mathsf{2Al^{3+} + 3H_2O} 		No reaction
Adding NaOH No reaction No reaction \mathsf{Al_2O_3 + 2OH^- + 3H_2O}

\mathsf{\longrightarrow 2Al(OH)_4} 		\mathsf{SiO_2 + 2OH^- \longrightarrow}

\mathsf{SiO_3^{2-} + H_2O}
Nature Basic Oxide Basic Oxide Amphoteric Oxide Acidic Oxide
Conductivity Good Good Good None
Melting Point 1275 2852 2027 1610


Oxide P4O10
(or P4O6) 		SO3
(or SO2) 		Cl2O7
Adding H2O \mathsf{P_4O_{10} + 6H_2O \longrightarrow}

\mathsf{4H_3PO_4} 		\mathsf{SO_3 + H_2O \longrightarrow}

\mathsf{H_2SO_4} 		\mathsf{Cl_2O_7 + H_2O \longrightarrow}

\mathsf{HClO_4}
Adding HCl No reaction No reaction No reaction
Adding NaOH \mathsf{P_4O_{10} + 12OH^- \longrightarrow}

\mathsf{4PO_4^{3-} + 6H_2O} 		\mathsf{SO_3 + OH^- \longrightarrow}

\mathsf{SO_4^{2-} + H_2O} 		\mathsf{Cl_2O_7 + OH^- \longrightarrow}

\mathsf{2ClO_4^- + H_2O}
Nature Acidic Oxide Acidic Oxide Acidic Oxide
Conductivity None None None
Melting Point 24 17 -92


Explaining the physical properties

Conductivity for ionic solutions (Na2O->Al2O3) is due to ions in solution/molten state. SiO2 is network covalent - no charges therefore no significant conductivity. Others are covalent molecules therefore no conduction.

Melting point - stronger bonds when atoms can be arranged in a simple structure - MgO is highest, then Al2O3, Na2O (the ratio between the two atoms should be as close to 1 as possible). SiO2 is network covalent -> high melting point (but not as high as ionic bonding). The final 3 decrease in melting point due to decreasing polarity of molecules -> smaller dipole-dipole interactions.

Halides (assuming Cl...could replace with Br, I, F etc) : Ionic Chlorides -> dissolved in H2O with little reaction, Covalent Chlorides -> dissolve + react to form HCl.


\mathsf{NaCl: NaCl + H_2O \longrightarrow Na^+ + Cl^- + H_2O}


Good conductivity (ionic structure) MP = 801


\mathsf{MgCl_2: MgCl_2 \longrightarrow Mg^{2+} + 2Cl^-}


Good conductivity (ionic structure) MP = 714


\mathsf{Al_2Cl_6: Al_2Cl_6 + 6H_2O \longrightarrow 2Al(OH)_3 + 6HCl}


Poor conductivity (Network covalent) MP = 178


\mathsf{SiCl_4: SiCl_4 + H_2O \longrightarrow Si(OH)_4 + 4HCl}


No conductivity (Covalent molecular) MP = -70


\mathsf{PCl_3: PCl_3 + 3H_2O \longrightarrow H_3PO_3 + 3HCl}


\mathsf{PCl_5: 2PCl_5 + 6H_2O \longrightarrow 2HPO_3 + 10HCl}


No conductivity (Covalent molecular) MP = -112


S2Cl2 Not required


\mathsf{Cl_2: Cl_2 + H_2O \longrightarrow HCl + HClO}


(Exception : F2 is such a strong oxidizer : \mathsf{2F_2 + 2H_2O \longrightarrow 4HF + O_2})


No conductivity (Covalent molecular) MP = -101


MP - NaCl and MgCl2 -> decreases due to packing (as above), drops to Al2Cl6 (network covalent). Others are covalent molecules - decreases due to decreasing polarity (Cl2 higher due to more electrons - greater LDF ?)


13.2 D-block elements (first row)

13.2.1

Typical d-block elements are generally those exhibiting multiple oxidation states (in period 4, not Sc or Zn)


13.2.2

The multiple oxidation states of the d-block (transition metal) elements is due to the proximity between the 4s and 3d sub shells (in terms of energy). All transition metals exhibit a 2+ oxidation state (both electrons being lost form the 4s and all have other oxidation states...ie

V - +4, +5 (apparently we need to know only 2 of these...weird if you ask me...but include Fe...

Cr - +3, +6

Mn - +4, +7

Fe - +3


13.2.3

Ligands are the molecules which donate an electron pair to form a dative covalent bond with the central atom (thus forming a complex ion).


13.2.4

Complex ions are molecules which carry a charge. They are formed around a central atom, with other atoms (or molecules) donating an electron pair to form a covalent bond to this central atom. Examples...

[Fe(H2O)6]3+ - Fe is the central atom, H2O is the ligand

[Fe(CN)6]3- - Fe is the central atom, CN is the ligand

[CuCl4]3- - Cu is the central atom, Cl is the ligand

[Cu(NH3)4]2+ - Cu is the central atom, NH3 is the ligand

[Ag(NH3)2]+ - Ag is central atom, NH3 is the ligand


13.2.5

The color in the transition metals (d-block) is predominantly due to the splitting of the d shell orbitals into slightly different energy levels. As a result, certain wavelengths of energy can be absorbed by the d-block elements (with electrons jumping between these slightly different energy levels), resulting in the complement color being visible.


13.2.6

d-block elements make good catalysts due to their multiple oxidation states (hence their ability to react with different species and produce a path of lower activation energy, and so allow the reaction to proceed at a faster rate). Examples...

MnO2 in decomposition of hydrogen peroxide

V2O5 in the contact process

Fe in Harber process

Ni in conversion of alkenes to alkanes


Comments

Retrieved from "http://thestudentroom.co.uk/wiki/Revision:Periodicity_-_13"
Article Tools:  Create New Article  |  Report This Article  |  This Article's History  |