Classification of Elements and Periodicity in Properties

Chemistry · Class 11

Simulation · Chemistry · Class 11

From configuration to place in the table

From the lesson The s, p, d and f blocks in Classification of Elements and Periodicity in Properties. Change the values and watch what happens.

From configuration to place in the tableChemistry · Class 11

The idea behind it

NCERT §3.6.1-3.6.4

  • The block is named after the kind of orbital receiving the last electron. Two exceptions: helium (1s²) belongs to the s-block but sits with group 18 because its shell is full; hydrogen (1s¹) can lose an electron like group 1 or gain one like group 17, so it is placed on its own at the top.
  • s-block: groups 1 (alkali metals, ns¹) and 2 (alkaline earth metals, ns²). Reactive metals with low ionization enthalpies, forming 1+ or 2+ ions; metallic character and reactivity rise down the group, so they never occur free. Their compounds are mainly ionic, except those of Li and Be.
  • p-block: groups 13 to 18, outer configuration ns²np¹ to ns²np⁶. The s- and p-blocks together are the representative or main group elements.
  • Each period ends in a noble gas, ns²np⁶; its full valence shell is hard to disturb, so reactivity is very low. Before them come the halogens (group 17) and chalcogens (group 16), with strongly negative electron gain enthalpies; they readily take one or two electrons to reach a noble gas configuration.
  • d-block (transition elements): groups 3 to 12, filling inner d orbitals; general configuration (n−1)d¹⁻¹⁰ns⁰⁻², with Pd (4d¹⁰5s⁰) the exception. All are metals, mostly with coloured ions, variable oxidation states and paramagnetism, and are often catalysts.
  • Zn, Cd and Hg, with (n−1)d¹⁰ns², miss most typical transition-metal features. Sitting between the very active s-block metals and the less active groups 13 and 14, the d-block acts as a bridge, which explains the name transition elements.
  • f-block (inner transition elements): lanthanoids Ce (58) to Lu (71) and actinoids Th (90) to Lr (103), outer configuration (n−2)f¹⁻¹⁴(n−1)d⁰⁻¹ns². All are metals, and members of one series are very alike.
  • Early actinoids have more complex chemistry than the matching lanthanoids because they show many oxidation states. Actinoids are radioactive, many made only in nanogram amounts or less; elements after uranium are the transuranium elements.
  • Predicting from the table: Z = 117 falls in group 17, [Rn]5f¹⁴6d¹⁰7s²7p⁵; Z = 120 would be in group 2, [Uuo]8s².