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Electronic configuration

Electronic configuration. D-block transition metals (p54 lts) incomplete d subshell in at least one of their ions* lose 4s electrons before 3d electrons when form ions. 4s orbitals filled before 3d orbitals except chromium ([Ar] 3d 5 4s 1 ) and copper ([Ar] 3d 10 4s 1 ).

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Electronic configuration

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  1. Electronic configuration • D-block transition metals(p54 lts) • incomplete d subshell in at least one of their ions* • lose 4s electrons before 3d electrons when form ions • 4s orbitals filled before 3d orbitals except chromium ([Ar] 3d5 4s1) • and copper ([Ar] 3d10 4s1)

  2. Oxidation States - rules • for uncombined elements, the oxidation number is zero • e.g. O in O2 gas, metallic sodium. • single atom ions, the oxidation state is the same as the charge on • the ion e.g. Mg2+ has an oxidation number of +2, I- is -1. • usually oxygen has an oxidation number of -2 and hydrogen +1. Exceptions • are peroxides (-1 for O) and metal hydrides (-1 for H). • fluorine, in its compounds, has an oxidation number of -1. • the algebraic sum of all oxidation numbers in a molecule must equal zero. • in polyatomic ions, the algebraic sum of all oxidation numbers must equal the charge on the ion.

  3. Transition metals According to the Aufbau principle, are 3d or 4s orbitals occupied first? Which 2 transition metals have electron configurations that do not follow 1. What is the definition of a transition metal? Which 2 metals aren’t technically transition metals? Transition metals lose electrons firstly from which sublevel when forming ions? What is the oxidation number of sulphur in SO32-? In metal hydrides, what is hydrogen’s oxidation number? What is the oxidation number of free elements?

  4. Oxidation and reduction Increase in oxidation number - oxidation of the species has occurred e.g. SO32- to SO42- Decrease in oxidation number - reduction of the species has occurred e.g. Cr2O72- to Cr3+ Compounds with metals in - high oxidation states tend to be oxidising agents - low oxidation states tend to be reducing agents

  5. Variable oxidation states Transition metals exhibit variable oxidation states of differing stability +2 common oxidation state arising from loss of 4s electrons 3d subshells have similar energy levels to 4s so fairly easy to lose 3d electrons Changes in oxidation state of transition metals often characterised by a distinct change in colour (p57) Different ions in different oxidation states have different stabilities (p58)

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