Chemistry · Ch 2 — p-Block Elements-I
SUMMARY
SUMMARY
- The elements in which the last electron enters a 'p' orbital constitute the p-block elements.
- p-Block elements share the general electronic configuration ns² np¹⁻⁶; elements of a group share the same outer configuration and differ only in n.
- Descending a group, ionisation energy generally decreases and metallic character increases.
- Ionisation enthalpy in a given group is generally higher than the corresponding element of the previous group, as expected.
- Descending group 13, electronegativity first decreases from boron to aluminium, then rises marginally.
- The first member of every p-block group differs from the rest of its family.
- In heavier post-transition metals, the outer ns electrons resist bonding -- the inert pair effect.
- Some elements exist in more than one crystalline/molecular form in the same physical state (e.g. carbon as diamond and graphite) -- allotropism.
- Borax is the sodium salt of tetraboric acid, obtained from colemanite ore by boiling with sodium carbonate.
- Boric acid can be extracted from borax and colemanite, and has a two-dimensional layered structure.
- The name alum is given to the double salt potassium aluminium sulphate, K₂SO₄.Al₂(SO₄)₃.24H₂O.
- Carbon occurs natively as graphite; silicon occurs as silica (sand and quartz) and in silicate minerals and clay.
- Catenation is an element's ability to form chains of atoms with itself.
- Recently discovered carbon allotropes -- graphene, fullerenes and carbon nanotubes -- extend the older diamond/graphite picture; nanotubes, in particular, have graphite-like tubes capped with fullerene ends.
- Silicones (polysiloxanes) are organosilicon polymers of formula (R₂SiO), classed as high-temperature polymers for their thermal stability. …