Atoms and reactions 1 Flashcards
What did Democritus come up with?
450BC
Suggested that if you divide matter enough times it eventually can no longer be divided as you would get a particle that wont split
What was Daltons atomic theory?
Early 1800s
atoms are tiny particles that make up elements
atoms cannot be divided
atoms of a given element are the same
atoms of one element are different from other elements
- created table of atomic masses
What did Joseph John Thomsen come up with?
1897-190 discovered that cathode rays were streams of particles called electrons they had a negative charge could be deflected by a magnet and electric field had a small mass this disproved Dalton and Democritus the negative charge= positive charge - plum pudding model
What was Ernest Rutherfords experiment?
1909-11
directed alpha particles towards a gold foil and measured the deflection
most of the particles did not deflect as expected
small percentage deflected at large angles
few deflected back to source
therefore
- positive charge and mass concentrated at centre in nucleus
- negative electrons orbit the nucleus
- most of the volume is between electrons and nucleus
- overall positive = negative charge
What did Niel Bohr come up with?
1913
altered Rutherford’s experiment and stated that electrons followed paths this explained
- spectral lines seen on emission spectra
- energy of electrons at different stands from nucleus
What did Henry Mosely come up with?
1913
discovered the link between x ray frequencies and elements atomic number
What did Rutherford discovery of the proton explain?
1918
- discovered the proton this explained how the atomic number was linked to x ray frequencies
atomic number=proton number
What did Louis de Broglie suggest?
1923
particles could have the nature of a wave
What did Erwin Schrodinger suggest?
1926
electrons had wave like properties in an atoms
atomic orbitals
What did James Chadwick discover?
1932, neutron
he obsereve a new type of radiation emitted from elements and showed it was made out of neutrons which had no charge and was the same mass as a proton
The modern atom
protons and neutrons are made out of quarks
What is the relative mass and charge of a proton?
1
1+
What is the relative mass and charge of a neutron?
1
0
What is the relative mass and charge of an electron?
1/2000
1-
What do isotopes have?
different mass number due to different number of neutrons
same number of protons and electrons therefore same atomic number
Why do isotopes react in the same way?
chemical reaction involve electrons and they have the same number of electrons, neutrons do not affect chemical reactions
What are isotope properties?
chemical = same physical = different due to different masses involved
What causes an ion?
when atoms lose or gain electrons and no longer have an equal number of protons and electrons
How do you work out charge?
proton-electron
What is the international standard for measurement of relative mass?
carbon-12
for an isotope what is the relative isotopic mass the same as?
mass number
why do you use the term weighted mass?
most elements contain a mixture of isotopes each in a different amount and different mass
What does the overall mass depend on?
the percentage abundance, relative mass of the isotope
How do you get the relative molecular mass? (simple molecules)
add together the relative atomic masses
How do you get the relative formula mass?(giant molecules)
add together the relative atomic masses
How do chemists count atoms?
the use a quantity called amount of substance for counting atoms
What is the amount of substance based on?
it is based on a standard count of atoms called the Avogadro constant this is the number of atoms per mole of the carbon-12 isotope
the mass of one mole….
is the relative atomic mass in grams
What is the empirical formula?
The simplest whole-number ratio of atoms of each element present in a compound
What is the empirical formula used for?
it is used for giant structures such as ionic compounds and giant covalent compounds
What is the molecular formula used for?
its used for compounds that are simple molecules
Definition of the molecular formula ?
the number and type of atoms of each element present in a molecule
How do you work out the molecular formula?
use the empirical formula, must be the same as or whole number
What do we do with by-products?
considered waste and have to be disposed of they have potential environmental harm and waste of valuable resources
they are usually sold or used elsewhere
What does atom economy describe?
it describes the efficiency of a reaction in terms of all the atoms involved
What is the equation of atom economy?
molecular mass of desired product/sum of molecular masses of all products x 100%
How can atom economy benefit society?
reduce the amount of waste products and make it sustainable
What’s the difference between atom economy and percentage yield?
percentage yield tells us the efficiency with which reactants are converted into products whereas atom economy tells us the proportion of desired products compared with all products formed
What is a addition reactions?
What is the atom economy of addition reactions?
2 or more reactants join together
100%
What is a substitution reaction?
What is the atom economy of substitution reactions?
1 or more atoms or molecules swapping places with another
less than 100%
What is a elimination reaction?
What is the atom economy of an elimination reaction?
removal of a small molecule (usually water) from another molecule
less than 100%
what do atoms of metals in group 1-13 do? (balancing charges)
loose electrons and form positive ions
what do the transition metals do (balancing reactions)
e.g. nickel(11) has 2+ charge
what happens in group 15-17
gain electrons and form negative ions
what happens to Be, B, C, Si
do not usually form ions as it requires too much energy to transfer the outer shell electrons to form ions
what are molecular ions?
groups of covalently bonded atoms that can lose or gain electrons to form ions
what ions have a 1+ charge
ammonium NH4+
Ag+
What ions have a 1- charge
hydroxide - OH -
nitrate - NO3-
What ions have a 2- charge
carbonate CO32-
sulfate SO42-
How can you predict formulae?
overall charges must be o
What ions have a 2+ charge
Zn2+
define relative isotopic mass
this is the mass of an atom of an isotope compared with 1/12 the mass of an atom of carbon-12
Define relative atomic mass
this is the weighted mean mass of an atom of an element compared with 1/12 the mass of an atom of carbon -12
Uses of mass spectrometry
- determination of relative isotopic mass and the relative abundances of the isotope
- calculation of the relative atomic mas of an element from the relative abundances of its isotopes
