3.1.1 Atomic Structure Flashcards
determine the number of fundamental particles in atoms and ions using mass number, atomic number and charge
- mass numer (A) - protons + neutrons
- Atomic number (Z) - protons/electrons in nucleus
-mass/charge
- proton - +1 / 1
- electron - -1/1/2000
-neurons-0 / 1
explain the existence of isotopes.
ions - different electrons/protons - e.g O2- , 10 electrons(gain 2 electrons) 8 protons
Na+, 10 electrons (lost 1 electron),11 protons
isotopes - elements same protons different neutrons
The principles of a simple time of flight (TOF) mass spectrometer, limited to ionisation, acceleration to give all ions constant kinetic energy, ion drift, ion detection, data analysis
- Vaporisation - sample vapourised - travel through tof spectrometer
- ionisation - sample pushed through nozzle making high-pressure jet, high voltage pass through - loss of electrons, gaseous - charge sample made (electrospray ionisation )
- acceleration - + ions through an electric field - lower mass/charge ratio quicker
- Ion drift - particles travel with constant KE and speed - drift - lower m/z ratio faster
- Detection - ions are, as electrical current when hits plate - lower m/z reach detector first - fastest
Mass spectrometer uses:
- identify elements , determine relative molecular mass , relative isotopic mass/abundance
interpret simple mass spectra of elements
- y-axis - m/z ratio, most +1 charge
- x-axis - abundance, %/nominal
value, %= add up to 100
- spectra(percentage on line ) - 2 isotopes of one element - e.g. 75% isotopes mass 35, 35% mass 37
- molecules (M+1 peak same as relative molecular mass of molecule )
calculate relative atomic mass from isotopic abundance, limited to mononuclear ions.
calculate relative atomic mass from isotopic abundance, limited to mononuclear ions.
electron configuration
- Electron configurations of atoms and ions up to Z = 36 in terms of shells and sub-shells (orbitals) s, p and d.
- s(2),p(6),d(10),f(14)
- 4s filled before 3d & lose from 4s first - lower energy (except Cr,Cu - lose from 4s move to 3d -more stable )
first ionisation energy
The minimum amount of energy required to remove 1 mole of electrons from 1 mole of atoms in a gaseous state
- endothermic process- +
-shielding/atomic size - more shells/bigger atom - weaker attraction - less energy to remove electron
-nuclear charge - more protons - greater attraction - more energy remove an electron
successive ionisation energy
- removal of more than 1 electron from same atom
- 2nd ionisation - more energy
-jumps in energy - remove electrons from shell close to the nucleus - along the axis more energy - 3,2,1
explain how first and successive ionisation energies in Period 3 (Na-Ar) and in Group 2 (Be-Ba) give evidence for electron configuration in sub-shells and in shells
first ionisation group 2 - decreases down group - atomic radius /shielding increase - electron further from the nucleus, weaker attraction, decrease the energy required
first ionisation period 3 - increases across period - increase proton/nuclear attraction - shielding similar -more energy remove outer electron
Al - decrease ionisation - outer electron on 3p sub-shell, higher energy sub-shell/further from the nucleus
S - decrease - electron repulsion - 3p orbital outer electron - electrons repel the same orbital - less energy to remove than phosphorus
History of the atom
1803 john Dalton - atoms are spheres and each element is made from different spheres
1897 jj thomson - Discovered in the electron . The atom wasn’t solid - other particles - plum pudding model
1909 Ernest Rutherford - discovered nucleus - very small , + charged - atom mostly empty space
1913 Niels Bohr - problem with ernest model - electrons could collapse into positive nucleus - there on fixed energy shells
Gold leaf experiment - + alpha particles - thin gold leaf - most went through , some deflected
experimental proof- EM radiation absorbed - electrons move between cells - emit radiation when move down to lower energy shells
