1.01 atomic structure

• how did John Dalton change the idea of the atom?

  John Dalton (1808) confirmed Democritus saying atoms are tiny solid balls. he didnt change the atom but created the first atomic theory that stated: • atoms are tiny invisible particles. • atoms of one element are the same. • compounds are formed by combining atoms.
• how did JJ Thomson change the idea of the atom?

  JJ Thomson (1897)discovered electrons with cathode rays. created the plum pudding model, which is a spherical change os positivity with embedded electrons.
• how did Earnest Rutherford change the idea of the atom.

  Earnest Rutherford (1911)conducted the gold foil experiment where he sent a beam of alpha particles at a thin sheet of gold. according to the plum pudding model, the positive particles should pass straight through (at most deflecting a little) however the results were surprising as some passed through, some deflected, and some came straight back. from this he concluded there must be a dense positive nucleus and the rest empty space. however this had flaws, according to coulomb if the electrons were free they would spiral into the nucleus.
• how did Niels Bohr change the idea of the atom?

  Niels Bohr (1913)electrons move in fixed energy levels and each atom has a certain number of levels.
• how did Erwin Schrödinger and Werner Heisenberg change the idea of the atom?

  electron clouds were created, locations that electrons had a high possibility of being in. this had flaws, the nucleus had twice the mass it was supposed to.
• how did James Chadwick change the idea of the atom?

  James Chadwick (1932) discovered the neutron.
• what is the mass and charge of a proton.

  mass : 1 charge : +1
• what is the mass and charge of a neutron?

  mass : 1 charge : 0
• what is the mass and charge of an electron?

  mass : 1/2000 charge : -1
• which is on top, mass or atomic number?

  mass number
• what is mass number?

  protons + neutrons
• what is atomic number?

  number of protons
• number of protons is the same as?

  number of electrons
• All atoms of an element have the same number of?

  protons
• define first ionisation energy

  the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
• define successive ionisation energy

  the energy required to remove 1 electron from each ion in one mole of gaseous n+ ions to form one mole of gaseous n+1+ ions
• how do you prove shell structure from a graph

  within each shell the ionisation energy increases as the ion is getting increasingly positivebig jumps are made when a new shell is broken into because it is closer to the nucleus
• how do you interpret group number from a graph?

  the number of electrons removed before the first big jump
• how do you interpret electronic structure from a graph?

  count the number of electrons right to left
• what does high ionisation energy mean?

  there is a high attraction between the positive nucleus and the outermost electron, so more energy is needed to remove the electron
• what three factors affect ionisation energy?

  • nuclear charge• electron shielding• distance
• how does nuclear charge affect ionisation energy?

  more protons results in a greater nuclear charge so there is a stronger nuclear attraction on the outermost electron so more energy is needed to remove it
• how does electron shielding affect ionisation energy?

  more shells results in greater electron shielding of the outermost electron from the nucleus so there is a weaker nuclear attraction therefore less energy is needed to remove the outermost electron
• how does distance affect ionisation energy?

  more shells results in a greater distance of the outermost electron to the nucleus so there is a weaker nuclear attraction and less energy is needed to remove the outermost electron.
• what are trends in 1st ionisation energy going across a period?

  outermost electron is in the same shell (so shielding and distance remains constant). the increasing number of protons increases the nuclear charge so the nuclear attraction is stronger to the outermost electron and more energy is needed to remove it
• what are the exceptions in increasing 1st ionisation energy going across a period?

  • drop between group 2 and 3 because the 3p subshell has a slightly higher energy than 3s so its further away and experiences slightly more shielding• drop between 5 and 6 because less energy is needed in group 6 as the electrons are paired and therefore experience repulsion
• what is the formula for kinetic energy?

  KE = 1/2mv^2 (J)
• what is the formula for velocity?

  v = d/t v = sqrt (2KE/m) (m/s)
• what is the formula for distance?

  d = v * t d = sqrt (2KE/m) * t (m)
• what is the formula for time?

  t = d/v t = d / sqrt (2KE/m) (s)
• what is the formula for mass?

  m = 2KE/v^2 m = Mr/1000/6.022 * 10^23 (kg)
• what is the formula to find time when distance and kinetic energy are the same?

  m1/t1 = m2/t2 t2 = sqrt (m2/m1) * t1
• what are the two types of ionisation?

  electron impact and electrospray
• what is electron impact ionisation?

  the sample is vapourised and electrons are knocked out by an electron gun to give each atom a 1+ charge
• when do you use electron impact ionisation?

  when the sample is an element or small molecule as it would just break large molecules apart
• what is electrospray ionisation?

  the sample is dissolved in a volatile solvent then passed through a hypodermic needle attached to a high voltage (so it sprays and spreads) this will add a H+ proton from the solvent to the sample
• when do you use electospray ionisation?

  when the sample is a high Mr compound to avoid fragmentation
• why does the sample need a 1+ charge?

  • so its attracted to the negative plate (gives it kinetic energy)• so it can gain an electron and cause current which is measured to get results
• what happens in the electric field?

  the ions are accelerated so they have the same KE. the same KE and distance means that any difference in speed is due to weight. lighter ions travel faster
• what happens at the detector?

  positive ions gain an electron causing current (movement of electrons) which is what is measured to get results