Chapter 11 Modern Atomic Theory Chemistry B2A

Structure of atom Rutherford’s model - (Source of  particles) e-e- +

Electromagnetic radiation Energy is transferred by light.

Electromagnetic radiation Wave: Wavelength Frequency Speed

Electromagnetic radiation Wavelength (λ): distance from one wave peak to the next. λ = 6×10 -7 m λ = 1×10 -7 m Frequency ( ν ): number of peaks that pass a given point in one second. λ = c ν c: speed of light = 3.0 × 10 8 m/s

Electromagnetic radiation longer λ →lower ν shorter λ →higher ν λ Electromagnetic spectrum

Photon: a stream of tiny packets of energy. (smallest unit of electromagnetic radiation) Electromagnetic radiation longer λ (lower ν) → lower energy shorter λ (higher ν) → higher energy

Emission of energy by atoms Flame test Emitted photons (light) Energy of heat (or …)

Emission of energy by atoms Excited states Only certain energy changes are allowed. Energy levels are quantized. Only certain types of photons are produced. (lowest energy level)

Bohr model Electron orbits the nucleus in circles. Electrons are moving in only allowed energy levels.

Wave mechanical model of atom Electron acts as a wave. Electron does not orbit the nucleus in circles. Electrons move randomly; however, there is more chance to find them close to nucleus.

Principal energy levels Energy n=1 n=2 n=3 n=4 Sublevels:spdf s s s s p p p d d f Principal level 1 Principal level 2 Principal level 3 Principal level 4 ground state (lowest energy level) Orbital: is a region of space and can hold maximum 2 electrons

spxpx pypy pzpz 1s1s 4p4p 4d4d 3d3d 4f4f Principal level 1 Principal level 2 Principal level 3 Principal level 4 2s2s 3s3s 4s4s 3p3p 2p2p 1S 2S 3S

Orbital: is a region of space and can hold maximum 2 electrons magnetic field paired spins Pauli exclusion principle Two electrons can stay together even with their opposite charges.

s p d f = = =14 Sublevels:spdf PxPx PyPy PzPz

LevelOrbitals Maximum number of electrons 11s2 22s, 2p2 + 6 = 8 33s, 3p, 3d = 18 44s, 4p, 4d, 4f = d 3p 3s 2p 2s Principal energy levelOrbitals Energy Order of filling 1 1s

Electrons configuration: description of the orbitals that its electrons occupy. Orbital box diagrams H (1) 1s 1s 1 Electron configuration 1s He (2) 1s 2 Li (3) 1s 2s 1s 2 2s 1 C (6) 1s 2s 1s 2 2s 2 2p 2 2p x 2p y 2p z

Valence electrons: electrons in highest principal energy level. Valence level: outermost principle energy level Cl (17) 1s 2 2s 2 2p 6 3s 2 3p 5 7 valence electrons Ar (18) 1s 2 2s 2 2p 6 3s 2 3p 6 8 valence electrons C (6) 1s 2 2s 2 2p 2 4 valence electrons Ne (10) 1s 2 2s 2 2p 6 8 valence electrons Noble gases Filled valence level

Noble gas notation Li (3) 1s 2s 1s 2 2s 1 [He] 2s 1 F (9) 1s 2s 1s 2 2s 2 2p 5 [He] 2s 2 2p 5 2p x 2p y 2p z Si (14) 1s 2s 3s 2p x 2p y 2p z 3p x 3p y 3p z 1s 2 2s 2 2p 6 3s 2 3p 2 [Ne] 3s 2 3p 2

Elements in same column (group) have the same number of electrons in their valance levels. Same chemical and physical properties. Only valance electrons are involved in chemical bond and chemical reactions. Inner electrons (core electrons) are not involved.

Lewis dot structure H Li C Cl 1A 2A 3A 4A 5A 6A 7A 8A He Only for main-group element: # of group = # of valance electrons

Main groups elements s, p Transition elements s, p, d Inner transition elements s, p, d, f

Orbital filling order Hf (72):1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 2 1s 2s2p 3s3p3d 4s4p4d4f 5s5p5d5f 6s6p6d6f 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s [Xe] 6s 2 4f 14 5d 2

Atomic Size Size of atom: is the size of its outermost occupied orbital. d

Ionization Energy Li + energy → Li + + e - ion Ionization energy: the energy required to remove the most loosely held electron from an atom in the gaseous state. Ionization energy