chapter 1,2,3 Flashcards
features of an atom
nearly all of atom’s mass in nucleus
atoms contain same number of protons and electrons
charges cancel
atomic number
number of protons
every atom of same element has same number of protons
isotopes
atoms of the same element with different numbers of neutrons and different masses
reactions of istopies
isotopes of same element have same number of electrons
number of neutrons has no effect on reactions
different isotopes of an element therefore react in the same way
properties of isotopes
higher mass isotopes:
- higher MP, BP and density
cations
positive ions
fewer electrons than protons
anions
negative ions
more electrons than protons
relative isotopic mass
mass of an isotope relative to 1/12th of the mass of an atom of carbon 12
relative atomic mass
weighted mean mass of an atom of an element relative to 1/12th the mass of an atom of carbon-12
weighted mean mass
accounts for percentage abundance of isotope and the relative isotopic mass of each isotope
mass spectrometer
determines percentage abundance of isotopes
ions detected on a mass spectrum as a mass to charge ratio
mass spectrometer process
sample placed in MS
sample vaporised and ionised to form positive ions
ions accelerated, heavier ions move more slowly and are more difficult to deflect than lighter ions
ions of each isotope are separated in this way
ions then detected on mass spectrum by mass to charge ratio
the greater the abundance, the larger the signal
avogadro’s constant
6.02x10^23
number of particles in one mole of a substance
molecular formula
number of atoms of each element in a molecule
empirical formula
simplest whole number ratio of atoms of each element in a compound
molar gas volume
volume per mole of gas molecules at a stated temperature and pressure
24dm^3
ideal gas equation
pV= nRT
pressure, Pa
volume m^3
R, ideal gas constant, 8.31 Jmol-1K-1
temperature, K
ideal gas equation assumptions
random motion
elastic collisions
negligible size
no intermolecular forces
reasons for low % yield
reaction may not have gone to completion
side reactions could have taken place
purification of the product may result in loss of some product
limiting reagent
the reactant that will be used up first and stop the reaction, not in excess
atom economy
measure of how well atoms have been utilised
HIGH: large proportion of desired products produced and few unwanted waste products
important for sustainability as they make best use of natural resources
