The S-Block Element: S Block Elements, Periodic Trends in Properties of Elements (For CBSE, ICSE, IAS, NET, NRA 2022)

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The S-Block Elements
  • The group 1 and group 2 elements of the periodic table are called the s-block elements.
  • The group 1 elements are alkali metals, and the group 2 elements are alkaline earth metals
  • They are named so because of the alkaline nature of the hydroxides and oxides.
  • Alkaline earth metals are characterized by two s-electrons, whereas alkali metals by one s-electron in the valence shell of their atoms.
  • These metals form mono positive and dispositive ions and are extremely reactive.

S Block Elements

  • The s block elements having only one electron in their s-orbital are called group one or alkali metals whereas the s block elements having two electrons filling their s-orbital are called group two or alkaline earth metals.
  • The s-block in the periodic table of elements occupies the alkali metals and alkaline earth metals, also known as groups 1 and 2.
  • The electrons present in an atom occupy various sub-orbitals of available energy levels in the order of increasing energy.
  • The last electron of an atom may find itself in either of the s, p, d, and f subshells.
  • Helium is also part of the s block. The principal quantum number “n” fills the s orbital.
  • Accordingly, the elements of the atom having their last valence electron present in the s-suborbital are called the s block elements.

Periodic Trends in Properties of Elements

Periodic Trends in Properties of Elements - a Plus Topper
  • Periodic trends are specific patterns in the properties of chemical elements that are revealed in the periodic table of elements.
  • Major periodic trends include electro negativity, ionization energy, electron affinity, atomic radii, ionic radius, metallic character, and chemical reactivity.
  • Alkali metal – These metals are silvery-white, low melting, soft and highly reactive.
  • Ionic size as well as the atomic size increases downs the group. On the other hand, the ionization enthalpies decrease down the group.
  • These compounds are mostly ionic.
  • Hydroxides and oxides dissolve in water to form strong alkalies. Some compounds of sodium are sodium chloride, sodium hydrogen carbonate, etc.
  • Manufacturing of Sodium hydroxide is done by the Castner-Kellner process and manufacturing of sodium carbonate is done by the Solvay process.
  • Alkaline earth metals – Metals have increased cationic charges. Their ionic size, as well as atomic size, is reduced.
  • Hydroxides and oxides of alkaline earth metals are less basic.
  • Some compounds of calcium are calcium carbonate, calcium hydroxide, etc.
  • Diagonal relationship – The first element of group 1 and the second element in group 2 show similar properties i.e. Lithium from group 1 and Beryllium in group 2.
  • So, similarities are called diagonal relationship.