IB chem S2.1, S2.3, S2.4

how are ionic compounds formed

when electrons are transferred from one atom to another to form ions with a complete outer shell of electrons

how does an ionic bond work

the positive and negative ions (cation and anion) are attracted to one another by electrostatic forces and build up into a strong lattice

why do ions have high melting points

a very large amount of energy is needed to break the electrostatic forces of attraction between them

how to name ionic compounds

cation-anion+ide

anions are sometimes known as —- because

acid radicals; they are formed when an acid loses one or more H+ ions

what is the ionic bond

the sum of all the electrostatic attractions and repulsions within the lattice

why are many ionic compounds water soluble

the energy given out when they are hydrated is enough to overcome the forces holding the ions together

what increases lattice enthalpy

the smaller the ions and the greater their charge

which ionic compounds can conduct electricity and why

molten or aqueous as they have free flowing ions but as a solid they are held in fixed positions

what is a metallic bond

the electrostatic attraction between a lattice of cations and delocalized electrons

what does the strength of a metallic bond depend on

the charge of the ions and the radius and the number of delocalized electrons

what is the metallic characteristic

the loss of control over the electrons in the outer shell

what are the properties of metals

good electrical conductivity

good thermal conductivity

malleable

ductile

high melting point

shiny

why are metals good electrical conductors

the delocalized electrons are mobile and so they can move through the metal structure in response to an applied voltage

why are metals good thermal conductors

the delocalized electrons are able to efficiently transfer thermal energy because they can move

why are metals malleable

there is non-directional movement of electrons so the lattice remains intact when pressure changes the conformation of the lattice

why do metals have high melting points

a lot of energy is required to overcome the electrostatic attraction in the metallic bond and separate the atoms

why are metals shiny

the delocalized electrons reflect light

what are transition elements

elements whose atoms have an incomplete d-sublevel or can give rise to cations with an incomplete d-sublevel

why do transition metals have high melting points

there is close energy proximity between the outer occupied sublevels so even the d-electrons can be delocalized which leads to a large number of delocalized electrons and a high positive charge that makes a strong metallic bond and high melting point

why do transition metals have high electrical conductivity

more delocalized electrons so more electrical conductivity

what is bonding described as

a continuum between the ionic, covalent and metallic models represented by a bonding triangle

how do you determine the type of bonding

electronegativity differences

how do you calculate the average electronegativity

E1+E2/2

what are alloys

mixtures of a metal and other metals or non-metals. They have enhanced properties

how are alloys produced

when you add a metal element to another metal in the liquid state, so that the different atoms can mix. When the mixture solidifies, the ions of the different metals are scattered through the lattice and form a structure of uniform composition

why is it possible to produce alloys

because of the non-directional nature of delocalized electrons and that the lattice can accommodate different size ions

why are alloys stronger

they are made up of different cations which interrupt to arrangement of the atoms and make it difficult for the atoms to slip over each other.

do alloys have fixed compositions

no

what kind of properties are retained when making an alloy and why

the metallic properties such as thermal and electrical conductivity or magnetism

what are polymers

large molecules or macromolecules made from repeating subunits called monomers

how do we show the structure of a polymer

a repeating unit

what are plastics

synthetic polymers

what are some properties of addition polymers such as plastic (5)

they have strong LDF depending on length

tend to be soft because the chains are not held in place very strongly

non-polar so they are usually water insoluble

unreactive because the chains are made of polyalkanes

lack delocalized electrons and free ions so they are thermal and electrical conductors

how do addition polymers form

the breaking of a double bond in each monomer

how do condensation polymers form

by the reaction between functional groups in each monomer with the release of a small molecule

how do you know id something will form a condensation polymer

it must have two functional groups where condensation can occur

when does a polyester form

when one monomer has two carboxylic acid groups and the other has two alcohol. this is an ester bond

when does a polyamide form

when one monomer has two carboxylic acid groups and the other has two amines and they form an amide bond

what is hydrolysis

the reverse reaction of condensation reaction where a water molecule is used to break the ester bond