Atoms and reactions Flashcards
What’s the structure of the plum pudding model
Negative electrons moving around in a ‘sea’ of positive charge. Neutral charge overall
What did Rutherford’s gold leaf experiment show?
positive charge of an atom and most of its mass is concentrated in a nucleus at the centre. negative electrons orbit the nucleus and most of the atom’s volume is the space between the nucleus and orbiting electrons
Where are protons and neutrons found?
in nucleus
what is the relative mass and charge of a proton, neutron and electron?
Proton = +1 charge, 1.0 relative mass Electron = -1 charge, 1/2000 relative mass Neutron = 0 charge, 1.0 relative mass.
What are isotopes of the same element?
elements with the same number of protons and electrons but different numbers of neutrons in the nucleus (and therefore different masses)
What is the atomic number
number of protons in the nucleus
what is the mass number
number of particles (protons and nuetrons) In the nucleus
Why do different isotopes of the same elements react in the same way?
chemical reactions involve electrons and isotopes have the same number + arrangements of electrons
neutrons make no difference to chemical reactivity
define relative isotopic mass
mass of an atom of an isotope compared with one-twelfth of the mass of an atom of carbon-12
define relative atomic mass
the weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12
which measurement of mass do you use when describing simple molecules
relative molecular mass
which measurement of mass do you use when describing giant structures
relative formula mass
What is mass spectrometry used to identify? 3 things.
identify an unknown compound
find the relative abundance of each isotope of an element
determine structural information about molecules
What is on the x and y axis for a mass spectrum graph? google if unfamiliar
y axis = percentage abundance
x axis = mass/charge ratio (m/z)
N.B. charge is usually 1
How can you predict the charge on an element’s ion from its position in the periodic table?
the number of electrons in the outer shell is the same as the group number of an element. e.g. lithium is in group one with one electron in its outer shell.
What elements don’t usually form ions and why?
Be, B, C and Si:
It requires too much energy to transfer the outer shell electrons to form ions.
Which elements form more than one ion?
iron (2+ and 3+)
copper (1+ and 2+)
What are molecular ions?
When groups of covalently bonded atoms can lose or gain electrons to form ions. The charge on a molecular ion can be considered as being shared out across the entire molecule.
What’s the formulae for these common molecular ions:
Ammonium Hydroxide Nitrate Carbonate Sulfate
Ammonium -> NH4 + Hydroxide -> OH - Nitrate -> NO3 - Carbonate -> CO3 2- Sulfate -> SO4 2-
What must the overall charge for an ionic compound always be?
Zero
What is Avogadro constant
number of atoms per mole of carbon 12 (6.02 x 10^23)
What equation links together molar mass, mass and moles?
mass = moles x molar mass
What’s an empirical formula?
the ratio between elements rather than the actual number of atoms of each elements.
Why is empirical formula used for giant structure compounds?
showing the actual formula would run into the millions of millions -> too big and complicated so we simplify it down to the most basic ratio
What is molecular formula?
molecular formula tells you the number of each type of atom that makes up a molecule
What is the molar gas volume?
the volume per mole of a gas. At room temperature and pressure, the molar volume is approximately 24.0dm^3mol^-1
What is the ideal gas equation (GIVE THE STANDARDISED UNITS)
PV=nRT` Pressure = Pascales Volume = Cubic metres Temperature = Kelvin R = Always 8.314 (will be given to you in questions)
Define concentration
amount of solute in mol dissolved per 1 dm^3 of solution
Define standard solution
solution of known concentration. usually used in titrations to determine unknown information about another substance.
What does 2M mean?
2mol dm^-3 concentration
How do you calculate percentage yield?
actual amount in mol of product / theoretical amount in mol of product
x 100
what are limitations of percentage yield
doesn’t take into account waste products formed
how do you calculate atom economy
molecular mass of the desired product / sum of molecular masses of all products
x 100
What does a high atom economy describe?
reaction that uses atoms with minimal waste.
