Topic 2 Atomic Structure
subatomic particles [40] 99.9% of mass of atom is located in nucleus, volume of electron cloud is 10,000 times greater than nucleus particle proton neutron electron Relative mass 1 Relative charge +1 -1 Location nucleus Shells around nucleus
Mass number, atomic number, isotope [41] Mass number (A) = sum of number of protons + neutrons Atomic number (Z) = number of protons (equals number of electrons in atoms, not ions), gives identification of atom Isotope = atoms with the same atomic number, different mass numbers (different number of neutrons)
Symbols for isotopes [41] C-12 Carbon-12 126C Exercises 2-4 page 46
Isotopes [42] Same chemical properties Different physical properties Mass Density Rate of diffusion Boiling and melting points
Radioisotopes [42-44] Unstable isotopes Uses Carbon dating (C-14) Medical tracers (I-125 and I-131) Radiation therapy (Co-60)
Mass spectrometer [47-49] Instrument which separates particles according to their masses and records the relative proportions Used in atomic mass determination
Mass Spectrometer [47]
Mass spectra [48] X- axis is relative mass relative mass = m/z where m= mass and z=charge
Atomic mass [48] Defined as the weighted average of all the isotopes of each element. Exercises 5-8 page 49
Knowledge of electron arrangements came about when studying the electromagnetic spectrum
Bohr model [52-53]
Bohr model [52-53]
Continuous vs. line spectrum [51]
Line spectra of hydrogen [52-53] Evidence of Bohr model of atom Spectrum of hydrogen is simplest – Why? Divided into distinct series Lyman UV region Balmer Visible region Paschen Infrared region
Line spectra of hydrogen [52-53]
Ionization energy and electron arrangement [54-57] Up to this point only main energy levels Ionization energies prove existence of main energy levels and sublevels Define ionization energy - Successive ionization energies -
Ionization energy and electron arrangement [54-57] main energy levels !
Ionization energy and electron arrangement [54-57] energy sublevels !!
Atomic Orbitals [59-61]
Atomic Orbitals [59-61]
Atomic Orbitals [59-61]
Atomic Orbitals [59-61]
Electron arrangement [56-64] Energy levels
Electron arrangement [56-64] Energy sublevels – Aufbau principle
Electron arrangement [56-64] orbitals– Hund’s rule Pauli exclusion principle
Electron arrangement [56-64] Electron configuration –
Electron arrangement [56-64]
Topic 2 practice Starting with worked example page 56 then continue with exercises 9-26