2.1- ionic model Flashcards
cations
metal atoms lose electrons they form positive ions= cations
anions
when non-metal atoms gain electrons they form negative ions called anions
why do atoms bond together
to achieve a decrease in their potential energy, this lower energetic state is more stable
how is this “lower energetic state” achieved
by atims attaining a full electron shell
what are the 3 types of electronic interaction resulting in 3 major types of bonding and what decides which type of bonding is used
which type of bonding occuring depending o the electronegativity of the atoms interacting with each other
ionic= low electronegativtity atoms (metals) interacting with high electronegativity atoms (non-metals)
covalent= both atoms have middle to high electroneagtivity (both non-metals)
metallic= bot atoms have low electronegativity (both metals)
what is used to define if bond is ionic or covalent
compare electronegativity difference between two atoms
greater than 1.7 units=ionic
less than 1.7 units=covalent
whats isoelectronic
when the atoms in an ionic bonding achieve the same electronic configuration as a noble gas
ionic bonding
electrostatic attractions between opositely charged ions
when ions have been formed what happens in an ionic bonding
when ions have been formed the electrostatic force of attraction between oppositley charged ions causes them to pack together into a 3dimensinal giant ionic lattice with every cation surrounded by anions and vis versa
why are the cations smaller than the metal atoms
because the cation has formed through the loss of the outermost energy level (valence shell) because the anion has formed by the gain of electrons they are bigger than the neutral atom due to increase electron electron repulsion adn expansion of the outer energy level. In general the cation is smaller than anion
ammonium cation
NH4+
sulphate anion
SO4,2-
carbonate anion
CO3,2-
nitrate anion
NO3-
phosphate anion
PO4, 3-
hydroxide anion
0H-
Hydrogencarbonate
HCO3-
do ionic susbtances conduct electricity
yes when molten or in solution, ions are free to move arund and can pass to the electrodes dipped in solution to become oxidised or reduced
do ionic susbtances have high melting or boiing point
yes, a large numer of ionic bonds must be broken to allow the ions to move around (a molten liquid_ or break free from the attractive forces completely (ionic gas)
are ionic substances hard and brittle
yes, does not bend, once sufficient force is applied the structure gives away completely and the material snaps
are ionic susbtances soluble
more soluble in polar solvents that have an uneven charge distribution(such as water) thhan non-polar solvents (such as hexane) the ions become surrounded by the polar solvent molecules and are dissolve
how is the strength of an ionic lattice measured
by its lattice enthalpy which is the energy recquired to break up a mole of an ionic lattice into gaseous ions under standard conditions
lattice enthalpy
enthalpy change when one mole of solid ionic compound is seperated into its gaseous ions.
the magnitude of the lattice enthalpy is a measure of
the stability of the ionic lattice 2 factors affect the stability:
size of the ions= smaller ions more closely the ions can pack together and attract each other
charge on the ion= the more charged is the ion the stronger is the electrostatic force of attraction between them
anions ending in -ate are
covalent groups of oxygen and another non-metal
where the metal name (cation group) comes first and ending f anion name changes to -ide
describe lattice enthalpy relationship with charge on cation adn anion
and with sum of ionic radii
directly porpotional to charge on cation adn cahrge n anion
inversely porportional to ionic radii
equation for lattice enthalpy
charge on cation x charge on anion/ sum of ionic radii
