3 Periodicity Flashcards
general trends across a period and down a group - atomic & ionic radii, melting points, first I.E. & E.A. and electronegativity
atomic radius: decreases across period, increases down group – increase in proton increases attraction (period), increase in energy level creates stronger electron repulsion (shielding effect) (group)
ionic radius: all ions increase in size down a group (outer level is further from shell) – ions decrease in size across a group (ion’s electrons stays constant, whilst proton number increases) – cations < anions (electron-proton difference)
melting points: m.p. depends on type of element (eg. group 1&2 metals, group 15-17 simple molecular structures) – m.p. depends on nuclear charge, determined by number of protons and strength of electron shielding
first I.E.: generally increases across period, decreases down group – generally as extra electrons fill same energy level as proton increases, increasing I.E. value. however, as sub-levels are filled with electron pairs, small amounts of electron repulsion created. hence paired electrons in sub-levels are easier to remove than orbitals with unpaired electrons.
first E.A.: decreases across a period, increases down a group –
first E.A. values are generally negative as atoms ‘want’ an extra electron. Atoms closer to achieving noble gas configuration tend to ‘want’ it more, hence causing first E.A value to be more negative
electronegativity: increases across period, decreases down group – electronegativity value tends to increase as size of atom decreases
