Chapter 5 ionic and covalent bonding and structure Flashcards
Ionic compound definition
The electrostatic attraction between positive ions and negative ions
Characteristics of ions
Oppositely charged ions attract each other strongly
The charge is spread over the whole ion so attracts the opposite from all directions
physical structure of ionic compounds
Form closely packed, regular ionic lattice
Structure of NaCl lattice
Each Na ion has six Cl ions surrounding it: 4 on the same layer and one above, one below. The same for Cl ions with Na
Melting and boiling points of ionic compounds
High bc req alot of energy to overcome strong electrostatic forces between ions
state of ionic compound at RT
solid
Melting and boiling point of ionic compounds increase/ strength of ionic bond increases as..
charges of ions increase in size, when size of ions involved decrease
Ionic compounds conduct when?
Molten or aqueous since ions are mobile charge carriers
Ionic compounds normally dissolve in..
..polar solvents
Covalent bonding?
Strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
What is a covalent bond in relation to atomic orbitals?
The overlap of orbitals, each containing one electron to give a shared pair of electrons
How do covalent bonds differ from the nature of ions attracting from all directions?
Covalent bons are localised, solely between the shared pair and the nuclei of the bonding electrons
Name for a shared pair of electrons?
A bonded pair
Name for a non-binding pair of electrons in a molecule?
Lone pair
HONC rules?
The number of covalent bonds formed by the following:
Hydrogen=1
Oxygen=2
Nitrogen=3
Carbon=4
Example of atoms that dont bond to adopt the structure of a group 8 atom
Boron triflouride, boron only has 3 outer shell electrons so can only bond to have a total of 6.
Compound which have expanded the octet
Native bonds?
A shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only. Uses an arrow in the displayed formula pointing away from the contributor
Average bond enthalpy?
A measure of covalent bond strength: larger values have a greater strength.
When is epansion of octet possible
In atoms with more than 2 shells (d block upwards) since there is only a max of 8 electrons available in the second shell
expanding the octet
when a previously spin paired electron jumps to a higher, available shell meaning that there are more electrons available to form covalent bonds
Why are ionic compounds solid at room temperature?
Insufficient energy to overcome strong electrostatic attraction between oppositely charged ions
Examples of elements that commonly expand the octet
Sulphur, Phosphorus, Chlorine
What dictates whether the octet is expanded and how many electrons are promoted?
the amount of energy supplied to the reaction
Which of covalent or ionic bonds are stronger?
Covalent
Carbon monoxide displayed formula
Two dashes between carbon and oxygen and one arrow leaving oxygen
Heat energy iss called?
enthalpy
Structure of ammonia?
Three single covalent bonds from N to Hs, one dative bond from N to H all in square bracket with plus charge
What can be used to represent extra ions in the dot cross diagram of negatively charged polyatomic ions?
A triangle
what are ions called when they are surrounded by water molecules (compound dissolved)
hydrated
When will ionic compounds didsolve
If energy released by hydration of ions is greater than or equal to the energy required to overcome ionic bonds in the giant lattice
