Download Topic 2 – Atomic Structure

Topic 2
Atomic Structure
subatomic particles [40]
particle
proton
neutron
electron
Relative mass
1
1
0
Relative charge
+1
0
-1
Location
nucleus
nucleus
Shells around
nucleus
99.9% of mass of atom is located in nucleus, volume
of electron cloud is 10,000 times greater than
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
•
12 C
6
• 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