CL 7- periodicity Flashcards
periodicity
definition
the repeating trend in chemical and physical properties across a period
first ionisation energy
definition
the energy required to remove one mole of electrons from one mole of gaseous atoms
first IE across periods 2 and 3
trend
- IE increases across a period
- atomic radius decreases
- stronger electrostatic attraction
- nuclear charge increases
- more energy required to remove outermost electron
anomalies IE at group 3 and group 6
group3
* decrease in IE
* outermost electron in group 3 in p subshell which is
* higher in energy and further from the nucleus (than s subshell)
group6
* decrease in IE
* electrons begin to pair in p subshell in group 6
* repulsion between paired electrons making 6th electron slightly easier to remove
IE down a group
trend
- IE decreases down group
- atomic radius increases
- (nuclear charge increases but)
- weaker electrostatic attraction
- less energy required to remove outermost electron
metallic bonding
definition
electrostatic attraction between positive ions and delocalised electrons
solid giant covalent lattice
atoms are held together by a network of strong covalent bonds in a giant lattice structure
why do metals have high melting points?
strong electrostatic attraction between positive metal ions and delocalised electrons which require a lot of energy to overcome
why are metals not soluble?
metals react with water instead of dissolving
why do metals conduct electricity?
delocalised electrons free to move
why do giant covalent compounds have high melting points?
strong covalent bonds which require a lot of energy to overcome
why are giant covalent compounds not soluble?
covalent bonds very strong, can’t be broken by interaction with solvents
variation in melting points across period 2/3
every group
increases from group 1 to group 3- higher positive charge, more delocalised electrons, stronger metallic bonding which require more energy to overcome
group 4- giant covalent structures so even higher increase, more energy required to overcome strong covalent bonds
decreases group 5- simple covalent structure, london forces require little energy to overcome. however the bigger the molecule the higher the melting point (S8 has higher melting point than P4)
