CHEM 101, Lecture notes Week 3
CHEM 101, Lecture notes Week 3 CHEM 101
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This 5 page Class Notes was uploaded by spencer.kociba on Wednesday October 12, 2016. The Class Notes belongs to CHEM 101 at Drexel University taught by Monica Ilies in Fall 2016. Since its upload, it has received 7 views.
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Date Created: 10/12/16
Spencer Kociba CHEM 101 Lecture notes Lecture 10/04/16 ● Bohr model of an atom ○ Developed model that explains how the structure changes during energy transitions ● Quantized=the atom can only have certain amounts of energy ● Orbitals, Shells and Transitions ○ Distances between rings are proportional and stationary ○ Electrons emit radiation when they fall down orbitals (higher to lower) ■ This emits a photon of light ○ “orbits”=shells ○ ‘orbitals”=subshells ○ higher→ lower=emission of energy ○ lower→ higher=absorption of energy ○ Quantum numbers determine shape, size and orientation in space of the orbitals (to describe both particle and wavelike behavior) ■ n=energy level ■ l=orbital type ■ m❑ =l position of orbital in an xyz plot ■ m❑ =s orientation of the spin of the electron ■ ^^^these are all the quantum numbers that completely describe the movement of the electron ○ Principal Quantum Number (n): The Energy Level ■ integer ≥ 1 ■ The larger “n” is, the higher energy in the orbital ■ The larger the value of “n”, the energy between orbitals lowers ○ Energies are described as negative ○ If energy=0, the electron escapes from the atom 1 ○ Energy❑ nR❑ ∙(h n2) ○ Each line in the emission spectrum corresponds to the difference in energy between the two energy states ○ ***electrons in high energy states are unstable and usually want to move to a lower state ○ For electrons in energy state n, there are (n1) energy states it can transition to ■ (can generate (n1) lines) ○ Energy❑ electronrgy❑ finalstategy❑ initial state 1 1 ○ Δ Energy=−R❑ H[ 2 − 2 ] n ❑ f n ❑i ○ Orbitals ■ 1st=s (groups 1 and 2) ■ 2nd=p (groups 1318) ■ 3rd=d (groups 312) ■ 4th=f (Atomic numbers 58103) Spencer Kociba CHEM 101 Lecture notes Lecture 10/04/16 ● Columns have the most common propertywise in the periodic table ● period=row (17) ○ also defines the number of orbitals ○ Except for the transition metals ● Transition elements= columns 312 (vary more than most elements) ● Shielding: only happens with the lower energy levels (core electrons) ○ When the lower energy levels experience the full nuclear charge, and the outer electrons experience less nuclear charge ○ Outer electrons cannot shield as efficiently as inner electrons ○ When an electron penetrates, it experiences less shielding and more nuclear charge ○ ● Penetration: when outer electrons overcome the force of the shielding and experiences the full nuclear charge ○ Before penetration ■ Shielding is occurring here ○ After penetration ■ Shielding is overcome ● Electron Configuration ○ Electrons fill up horizontally first with spin, after all the rows are filled then the electrons begin to pair up ○ As the number of shells increases, the energy increases ○ LEVELS OF ENERGY (increases from 1s to 4p) ● 4p ○ 3d ■ 4s ● 3p ■ 3s ● 2p ■ 2s ■ 1s ■ ■ ● Examples of elements and their electron configurations/orbital diagrams ○ Hydrogen and Helium do not experience shielding because there is only 1 orbital level ● #of orbitals depends on how many directions they can form ○ If all the electrons are paired, the element is nonreactive ○ Ex. s= (sphere in an xyz plane) so there is only 1 posibility/combination of orbital orientation=1 box in diagram ○ p=(several spheres along different axes in xyz plane), there are 3 different combinations of orientations so there are 3 boxes in the electron configuration diagrams
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