test Flashcards
What are the uses of mass spectrometry?
-Identify unknown compounds
-Find relative abundance of each isotope of an elemnt
-Determine structural information
How does a mass spectrometer work
-Sample is made into positive ions
-Passes through the apparatus and are separated according to mass to charge ratio
-Computer analyses the data and produces mass spectrum
what is an empirical formula
Simplest whole number ratio of atoms of each element present in a compound
orbital definition
a region of space around the nucleus where there is a high probability of finding an electron
outline s orbitals
-can hold 2 electrons
-have spherical shape
outline p orbitals
-can hold 2 electrons
-have dumbbell shape
outline s sub shells
-made from 1 s-orbital
-can hold 2 electrons
outline p subshels
-made from 3 p-orbitals
-can hold 6 electrons
outline d-orbitals
-can hold 2 electrons
-shells 3 and 4 contain
What is the Aufbau Principle
Fill in increasing order of energy
What is the Pauli Exclusion Principle
Electrons pair with opposite sound to stabilise the atom
What is Hund’s Rule
One electron occupies each orbital before pairing up
What produces a giant ionic lattice
Electrostatic attraction between the positive and negative ions
What is a giant ionic lattice
Generally crystals with straight edges, suggesting ions line up alternatively in repeating straight line.
Why is the melting point of ionic lattices so great?
A lot of energy is required to break the bonds so the ions can move apart and change state
What can increase melting and boiling points
As charge of the ions increase.
Outline the solubility or ionic lattices
-Relative strengths of the attractions within the lattice and between the ions and water molecules determine solubility
-An ionic compound where ions have large charges the ionic attraction may be too strong for water to break lattice stricter
What is a dative covalent bond
Both bonding electrons originate from the same atom
Isoelectronic species
Have the same electron configuration
Covalent molecule
Shared pair of electrons between atoms with strong electrostatic attraction between the shared pair of electrons and the nuclei of the bonded atoms
Lone pair
pair of electrons not involved in bonding
Trigonal planar
-3 Bond pairs
-120°
Linear
-2 bond pairs
-180°
Tetrahedral
-109.5°
-4 bond pairs
octahedral
-6 bond pairs
-90°
Trigonal Pyramidal
-5 bond pairs
-90°
-120°
Electron pair repulsion theory
Electrons exists in pairs in spaces we refer to as orbitals
They are all negatively charged so will repel other pairs if they get too close
Therefore electrons will take up positions as far away from each other as possible to minimise repulsion.
Lone pair rule for molecule shapes
-Lone pair + lone pair repulsion is greater than lone pair + bond pair repulsion which is greater than bond pair + bond pair repulsion
NH3 molecule shape
-trigonal pyramidal
-107°
H20 molecule shape
-non-linear
-104.5°
