Ionic Bonding Flashcards
what does ionic bonding consist of
- a regularly arranged array of oppositely charged ions
- extending throughout a giant lattice network
what does ionic bonding usually make
solid materials (and salts)
even though ionic compounds have ions of the same charge close to each other, why does their structure still remain
because the ions are arranged in such a way that the electrostatic attractions between the oppositely charged ions are greater then the repulsion between ions of the same charge
how do you determine the strength of ionic bonds
- by calculating the amount of energy needed
- in one mole of the solid
- to separate the ions to infinity
why ‘infinity’
because when they are that distance apart they can no longer interact
what are the units for this calculation
kJ mol-1
what are the two main factors that affect the amount of energy needed
- size of the ions
- charge of the ions
what is the relationship between the amount of energy required to separate the ions to infinity and the their size
a decrease in size results in more energy being required
what is the relationship between the amount of energy required to separate the ions to infinity and the their charge
an increase in the charge of both ions results in more energy being required
what is the trend in ionic radii as you go down group 1
as you go down group 1 their atomic radii increases
what is the trend in ionic radii as you go down group 7
as you go down group 7 their atomic radii increases
why do they increase in both cases
- because the number of electron shells they have increases
- so the ions would naturally get larger
what is the trend in ionic radii as you go across period 2 and 3
- they decrease
why does the ionic radii across periods decrease
- because across the period the number of electron shells isnt changing
- but the nuclear charge is increasing
- resulting in stronger electrostatic forces of attraction pulling the electrons towards the nucleus
- leading to a smaller ionic radius
why are the boiling points of ionic solids so high
- they consist of a giant lattice network of oppositely charged ions
- with so many ions being present, the combined electrostatic forces of attraction amongst them is very strong
- resulting in a large amount of energy being required to overcome them
why are ionic solids in the form of crystals brittle when stress is placed on them
- the layers of ions slide over each other due to the stress
- this causes ions of the same charge to be side by side and therefore repel each other
- making it easy for the crystal to break apart
why cant solid ionic compounds conduct electricity
- because there are no delocalised electrons
- the ions are also not free to move under the influence of a potential difference
when would an ionic compound only be able to conduct electricity and why
- when its in a molten or aqueous state
- because the ions would be fluid and free to move
- therefore being able to carry a current through them
why are ionic solids soluble despite their bonds being so strong
- the energy required to break the lattice structure and separate the ions
- can be supplied by the hydration of the separated ions produced
- this means that both positive and negative ions from the ionic solid are attracted to water molecules due to its polarity
how does the polarity and structure of water cause positive and negative ions to be attracted to it
- the oxygen atom in the water molecule has a partial negative charge
- so the oxygen end of the molecule would be attracted to positive ions
- the hydrogen atoms in the water molecule have partial positive charges
- so the hydrogen end of the molecule would be attracted to negative ions
what are cations and anions
- cation = positive ion
- anion = negative ions
when are cations and anions produced
- when an ionic compound is formed
- from the reaction between a metal and non-metal
what would be the dot and cross diagram of the reaction 2Na + Cl2 = 2NaCl
- you would draw the two Na atoms with one electron on their outer shell (crosses)
- the chlorine molecule consisting of two chlorine atoms with their outer electrons (dots)
- then show what they become after the reaction
- being [Na]+ [Cl(7 dots 1 cross)]- [Na]+ [Cl(7 dots 1 cross)]-
- twice because of the 2NaCl
what is the biggest evidence for the existence of electrons
electrolysis
how is electrolysis set up
you have a positive and negative electrode formed by a d.c. current placed into a molten / aqueous state of an ionic compound
if the ionic compound were to be sodium chloride, how would this electrolysis prove that ions are at play
- when a direct current is passed through the ionic compound, the positively charged sodium ions migrate to the cathode
- while the negatively charged chlorine ions migrate to the anode
- the sodium ions would gain electrons and be discharged as solid sodium
- while the chlorine ions lose electrons and is discharged as chlorine gas
what are the half equations for this happening to the sodium and chlorine atoms
- 2Na+ + 2E- = 2Na
- 2Cl- = Cl2 + 2e-
