Ch 4 Arrangement of Electrons in Atoms 4 Ch 4 Arrangement of Electrons in Atoms 4.1 The Development of a New Atomic Model Electromagnetic radiation: visible light, x-rays, UV, infrared, Gamma, radio, microwaves Electromagnetic spectrum

Wavelength: distance between corresponding points Frequency: # waves that pass a given point Photoelectric effect: when light strikes a metal, e- are released Quantum: E that can be gained/lost by an e- E=hv E is Energy v is frequency s-1 h is constant 6.626x10-34 J.s Photon has 0 mass and carries quantum of E

Ground state: lowest E Excited state: higher E potential Emission-line spectrum: see bands of colors Continuous spectrum: ex rainbow, see range of frequencies

Bohr’s Atomic Model e- circled nucleus on paths or orbitals Lowest energy state near nucleus When e- gets excited to moved up Energy level, called absorption When e- falls to lower Energy level, photon is emitted, called emission

4.2 The Quantum Model of the Atom De Brogile Light behaves both as a wave and particle e- have wavelike properties Diffraction: waves interfere; interference: waves overlap Heisenberg Heisenberg uncertainty principle: cannot know both position and velocity at same time Schrodinger Describes mathematically wave properties of e- quantum numbers: orbital Principal quantum number: main energy level; n 1-6 Angular momentum quantum number: shape/ s,p,d orbital Magnetic quantum number: 3-D/ x,y,z planes Spin quantum number: e- spin

Angular momentum quantum number: Shape of orbital Magnetic quantum number: m Orientation of orbital around nucleus

Number of orbitals in main E level increases with value of n Spin quantum number: + ½ or – ½ 2 e- per orbital The e- spin oppositely

4.3 Electron Configurations Aufbau Principle: fill lower energy levels first Pauli Exclusion Principle: no 2 e- can have same set of quantum numbers Hund’s Rule: fill all before pairing orbitals

Orbital Notation: arrow diagram Electron-configuration: writing it all out Noble-gas: [noble gas] with rest of e- written out Final Entry: exact location

Argon, Ar Potassium, K