ionic bonding Flashcards
ioic bonding
strong electrostatic force of attraction between oppositely charged ions in all directions in the lattice, formed by electron transfer
what is the structure of ionic crystals?
giant lattices of ions
what charge to metal atoms and non metal atoms form?
metal: positive ions
non-metal: negative ions
why is ionic bonding strong and why does it have higher melting points?
ions are smaller and/or have higher charges
why are positive ions smaller compared to their atoms?
it has one less shell of electrons and the ratio of protons to electrons has increased so there’s greater net force on remaining electrons holding them more closely
why are the negative ions from groups 5 to 7 larger than the corresponding atoms?
negative ion has more electrons than the corresponding atom but the same number of protons. so the pull of nucleus is shared over more electrons and the attraction per electron is less, making the ion bigger
why do N3-, O2-, F-, Na+, Mg2+, Al3+ all have the same electronic structure? (of the noble gas Ne)
there are increasing numbers of protons from N to F and then Na to Al, but the same number of electrons. the effective nuclear attraction per electron therefore increases and ions get smaller
why does the ionic radii increase down the group?
because as one goes down the group the ions have more shells of electrons
what do the contour lines mean?
equal electron density
how are the ions arranged in electron density map?
regular pattern
are chloride ions or sodium ions bigger?
chloride ions are larger than sodium ions
why are ions discrete or separate?
the electron density falls to zero between the ions
what doesn’t the electron density map show?
edge of the ion and so it is difficult to measure the radius of the ion from an electron density map
what are the physical properties of ionic compounds?
high melting points - strong attractive forces between the ions
non conductor of electricity when solid - ions are held together tightly and cannot move
conductor of electricity when in solution or molten - ions are free to move
brittle/easy to cleave apart
why are ionic compounds brittle/easy to cleave apart?
a little force will push the ions along and ions will be next to similar ions. there will be a force of repulsion between like ions, pushing the layers apart
why is the migration of ions presented as CuCrO4?
transition metals - they’re coloured
what colour are Cu2+ ions? and which electrode do they go to?
blue
negative electrode
what colour are CrO4 2- ions? and which electrode do they go to?
yellow
positive electrode
how do you do the potassium manganate solution test for ions?
- a drop of potassium manganate (purple) placed on moist filter paper on a microscope side
- ends of the slide are connected to a 24V DC power supply
- after 10 minutes the purple colour of the MnO4 - ion has migrated to the positive electrode
