Dr. S. M. Condren Chapter 8 Electron Configuration, Periodicity, and Properties of the Elements

Dr. S. M. Condren Electromagnetic Radiation Electromagnetic wave A wave of energy having a frequency within the electromagnetic spectrum and propagated as a periodic disturbance of the electromagnetic field when an electric charge oscillates or accelerates.

Dr. S. M. Condren

Electromagnetic Radiation Electromagnetic wave wavelength frequency amplitude

Dr. S. M. Condren

Quantum Mechanics Quantum theory the theory of the structure and behavior of atoms and molecules.

Dr. S. M. Condren Black Body Radiation

Dr. S. M. Condren Electromagnetic Radiation = c where  => frequency  => wavelength c => speed of light

Dr. S. M. Condren Electromagnetic Radiation E hi - E lo = hc/ where E => energy h => Planck's constant c => speed of light  => wavelength

Dr. S. M. Condren Photoelectric Effect the emission of electrons by substances, especially metals, when light falls on their surfaces.

Dr. S. M. Condren

Photons The quantum of electromagnetic energy, generally regarded as a discrete particle having zero mass, no electric charge, and an indefinitely long lifetime.

Dr. S. M. Condren

Line Spectrum A spectrum produced by a luminous gas or vapor and appearing as distinct lines characteristic of the various elements constituting the gas.

Dr. S. M. Condren Emission Spectrum The spectrum of bright lines, bands, or continuous radiation characteristic of and determined by a specific emitting substance subjected to a specific kind of excitation.

Dr. S. M. Condren Ground State The state of least possible energy in a physical system, as of elementary particles. Also called ground level.

Dr. S. M. Condren Excited State Being at an energy level higher than the ground state.

Dr. S. M. Condren

Absorption Spectrum Light shinning on a sample causes electrons to be excited from the ground state to an excited state wavelengths of that energy are removed from transmitted spectra

Dr. S. M. Condren Knowing diamond is transparent, which curve best represents the absorption spectrum of diamond (see below)? A, B, C

Dr. S. M. Condren The Atomic Spectrum of Hydrogen and the Bohr Model Bohr Model for the Hydrogen Atom mnr = nh/2p

Dr. S. M. Condren Bohr Model Netscape NCSU Materials Science site –Chapter 2 Atomic Bonding I Atoms and Electrons –slide 2 or or through the CHEM 115 homepage

Dr. S. M. Condren Bohr Atom

Dr. S. M. Condren Bohr Model E = -B/n 2 where n => quantum number 1, 2, 3, 4, 5, 6, 7, etc

Dr. S. M. Condren Bohr Model E = ( X J/part.) (6.022 X part./mole) (1 kJ/10 3 J)/n 2 = (-1312 kJ/mol)(1/n 2 )

Dr. S. M. Condren Bohr Model for hydrogen ground state: n = 1 excited state: n > 1

Dr. S. M. Condren

Line Spectra Lyman series => ultraviolet n > 1 ==> n = 1 Balmer series => visible light n > 2 ==> n = 2 Paschen series => infrared n > 3 ==> n = 3

Dr. S. M. Condren Line Spectra See CHEMWORKS software

Dr. S. M. Condren According to the energy diagram below for the Bohr model of the hydrogen atom, if an electron jumps from E1 to E2, energy is absorbed emitted not involved

Dr. S. M. Condren Heisenberg, Werner 1901–76, German physicist 1932 Nobel Prize in physics A founder of QUANTUM MECHANICS, he is famous for his uncertainty principle, which states that it is impossible to determine both the position and momentum of a subatomic particle (such as the electron) with arbitrarily high accuracy.

Dr. S. M. Condren Heissenberg Uncertainty Principle “ it is impossible to determine both the position and momentum of a subatomic particle (such as the electron) with arbitrarily high accuracy” The effect of this principle is to convert the laws of physics into statements about relative, instead of absolute, certainties.

Dr. S. M. Condren Orbitals region of probability of finding an electron around the nucleus 4 types => s p d f maximum of 2 electrons per orbital

Dr. S. M. Condren Pure Atomic Orbitals shape # of orbitals / energy level s spherical 1 p dumbbell 3 d complex 5 f very complex 7

Dr. S. M. Condren

Shapes of Orbitals

Dr. S. M. Condren

Electronic Configurations The shorthand representation of the occupancy of the energy levels (shells and subshells) of an atom by electrons.

Dr. S. M. Condren Electronic Configuration shells=>energy levels subshells=>orbitals

Dr. S. M. Condren Electron Filling Order Diagram 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s

Dr. S. M. Condren Electronic Configuration H atom 1 electron 1s 1

Dr. S. M. Condren Electronic Configuration He atom 2 electrons 1s 2

Dr. S. M. Condren Electronic Configuration Li atom 3 electrons 1s 2, 2s 1

Dr. S. M. Condren Electronic Configuration Cl atom 17 electrons 1s 2, 2s 2, 2p 6, 3s 2, 3p 5

Dr. S. M. Condren Electronic Configuration As atom 33 electons 1s 2, 2s 2, 2p 6, 3s 2, 3p 6, 4s 2, 3d 10, 4p 3 or [Ar] 4s 2, 3d 10, 4p 3

Dr. S. M. Condren Mn: [Ar]4s 2 3d ? How many d electrons does Mn have? 4, 5, 6

Dr. S. M. Condren Electronic Configuration negative ions add electron(s), 1 electron for each negative charge

Dr. S. M. Condren Electronic Configuration S -2 ion (16 + 2)electrons 1s 2, 2s 2, 2p 6, 3s 2, 3p 6

Dr. S. M. Condren Electronic Configuration positive ions remove electron(s), 1 electron for each positive charge

Dr. S. M. Condren Electronic Configuration Mg +2 ion (12-2)electrons 1s 2, 2s 2, 2p 6

Dr. S. M. Condren How many valence electrons are in Cl, [Ne]3s 2 3p 5 ? 2, 5, 7

Dr. S. M. Condren For Cl to achieve a noble gas configuration, it is more likely that electrons would be added electrons would be removed

Dr. S. M. Condren Magnetism Result of the spin of electrons diamagnetism - no unpaired electrons paramagnetism - one or more unpaired electrons ferromagentism - case of paramagnetism where the substance retains its magnetism

Dr. S. M. Condren paramagnetic ferromagnetic

Dr. S. M. Condren Trends in the Periodic Table atomic radius ionic radius ionization energy electron affinity

Dr. S. M. Condren Atomic Radius decrease left to right across a period –as nuclear charge increases, number of electrons increase; however, the nucleus acts as a unit charge while the electrons act independently, pulling electrons towards the nucleus, decreasing size

Dr. S. M. Condren Atomic Radius increase top to bottom down a group –each additional electron “shell” shields the outer electrons from the nuclear charge Z eff = Z - S whereZ eff => effective nuclear charge Z => nuclear charge, atomic number S => shielding constant

Dr. S. M. Condren Atomic Radius increases from upper right corner to the lower left corner

Dr. S. M. Condren

Ionic Radius same trends as for atomic radius positive ions smaller than atom negative ions larger than atom

Dr. S. M. Condren Ionic Radius Isoelectronic Series series of negative ions, noble gas atom, and positive ions with the same electronic confiuration size decreases as “positive charge” of the nucleus increases

Dr. S. M. Condren

Ge is a semiconductor. If half of the Ge atoms of a sample of Ge are replaced with Ga atoms, with what element should the other half of the Ga atoms be replaced in order for this new compound to be isoelectronic with Ge? Sn, As, Se

Dr. S. M. Condren Ionization Energy energy necessary to remove an electron to form a positive ion low value for metals, electrons easily removed high value for non-metals, electrons difficult to remove increases from lower left corner of periodic table to the upper right corner

Dr. S. M. Condren Ionization Energies first ionization energy energy to remove first electron from an atom second ionization energy energy to remove second electron from a +1 ion etc.

Dr. S. M. Condren

Electron Affinity energy released when an electron is added to an atom same trends as ionization energy, increases from lower left corner to the upper right corner metals have low “EA” nonmetals have high “EA”