Download Chapter 7: Quantum Mechanical Model of Atom

Quantum Mechanical Model of
Atom
Overview
• Atomic Spectra
• Nature of Matter & Energy
Atomic Spectra
• Absorption vs. Emission Phenomenon
– Absorption – energy is supplied to promote electrons from
ground state (lowest energy level) into higher energy levels
(excited states).
– Electrons prefer ground state (more stable).
Atomic Spectra
• Absorption vs. Emission Phenomenon
– Emission – excited electrons loses energy (usually by
emitting light) and returns to a lower energy state or the
ground state.
– Atoms give off light when heated or otherwise excited
energetically; thereby providing a clue as to their chemical
makeup.
Atomic Spectra
• Continuous Spectrum vs. Line Spectrum
– Continuous spectrum contains all wavelengths of visible
light. Observed as white light.
– Line spectrum contains specific wavelengths that result in
a unique “fingerprint” that is used to identify elements. No
two elements have the exact same line spectrum.
Atomic Spectra
Atomic Spectra
Atomic Spectra
• Wavelength values found using
Balmer-Rydberg Equation
• 1/λ = R [1 / m2 – 1 / n2]
• R = Rydberg Constant
• (R = 1.097 x 10-2 nm-1)
• The values (m & n) are integers
such that n>m
Nature of Matter & Energy
• Relationship between
energy, frequency, and
wavelength.
• Developed by two
physicists (Max Planck
& Albert Einstein)
Nature of Matter & Energy
• Max Planck proposed that matter & energy are not distinct in
nature; they can be looked upon as one in the same.
• Energy is only emitted in discrete packets called quanta.
• E=nhν=nhc/λ
h = 6.626 x 10-34 J sec
Nature of Matter & Energy
• Albert Einstein used the idea of quanta to
explain the photoelectric effect.
• He proposed that light behaves as a
stream of particles called photons.
• Also known for famous E = mc2
Nature of Matter & Energy
• Louis deBroglie – used work of Planck & Einstein to propose
the wave-particle duality concept.
• He suggested waves can behave as particles and particles can
behave as waves.
• For a particle
λ=h/mv
• For light
λ=h/mc