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Atomic Structure and Periodicity. Confused??? You’ve Got Company!. “ No familiar conceptions can be woven around the electron; something unknown is doing we don’t know what.”. Physicist Sir Arthur Eddington The Nature of the Physical World 1934. The Wave-like Electron.
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Confused??? You’ve Got Company! “No familiar conceptions can be woven around the electron; something unknown is doing we don’t know what.” Physicist Sir Arthur Eddington The Nature of the Physical World 1934
The Wave-like Electron The electron propagates through space as an energy wave. To understand the atom, one must understand the behavior of electromagnetic waves. Louis deBroglie
Wave-Particle Duality JJ Thomson won the Nobel prize for describing the electron as a particle. His son, George Thomson won the Nobel prize for describing the wave-like nature of the electron. The electron is a particle! The electron is an energy wave!
Electromagnetic radiation propagates through space as a wave moving at the speed of light. The Wave Like Electron c = C = speed of light, a constant (3.00 x 108 m/s) = frequency, in units of hertz (hz, sec-1) = wavelength, in meters
The Wave Like Electron Types of electromagnetic radiation:
Long Wavelength = Low Frequency = Low ENERGY Wavelength Table Short Wavelength = High Frequency = High ENERGY
Spectroscopic analysis of the visible spectrum… …produces all of the colors in a continuous spectrum
Spectroscopic analysis of the hydrogen spectrum… …produces a “bright line” spectrum
Electron transitionsinvolve jumps of definite amounts ofenergy. This produces bands of light with definite wavelengths.
Niels Bohr Proposed that the electron in a hydrogen atom moves around the nucleus only in certainallowed circular orbits.
The energy (E ) of electromagnetic radiation is directly proportional to the frequency () of the radiation. E = h E = Energy, in units of Joules (kg·m2/s2) h = Planck’s constant (6.626 x 10-34 J·s) = frequency, in units of hertz (hz, sec-1)
Relating Frequency, Wavelength and Energy Common re-arrangements:
Electron Energy in Hydrogen n = energy level ***Equation works only for atoms or ions with 1 electron (H, He+, Li2+, etc).
Calculating Energy Change, E, for Electron Transitions Energy must be absorbed from a photon (+E) to move an electron away from the nucleus Energy (a photon) must be given off (-E) when an electron moves toward the nucleus
Electron configuration of the elements of the first three series
Irregular confirmations of Cr and Cu Chromium steals a 4s electron to half fillits 3d sublevel Copper steals a 4s electron to FILL its 3d sublevel
ISOELECTRONIC SUBSTANCES and EXCITED STATES • Substances with the same number of electrons are isoelectronic ions. • Isoelectronic ions (or molecules) ions (or molecules) with the same number of valence electrons. • Isoelectronic substances: P3, S2, Cl, Ar, K+, Ca2+. • The electron configation of an element in an excited state will have an electron in a high-energy state E.g. [Ar]4s13d94p1 is an excited-state electron configuration for Cu.
Sizes of sorbitals Orbitals of the same shape (s, for instance) grow larger as n increases… Nodes are regions of low probability within an orbital.
The s orbital has a spherical shape centered around the origin of the three axes in space. s orbital shape
P orbital shape There are three dumbbell-shaped porbitals in each energy level above n = 1, each assigned to its own axis (x, y and z) in space.
Things get a bit more complicated with the five d orbitals that are found in the d sublevels beginning with n = 3. To remember the shapes, think of: “double dumbells” …and a “dumbell with a donut”!
