Woods Chem-1 Lec-04a 10-1 Elect Config (std) Page 1 STRUCTURE OF THE ATOM

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1 Woods Chem-1 Lec-04a 10-1 Elect Config (std) Page 1 STRUCTURE OF THE ATOM Neils Bohr: 1913 Developed the Bohr Model of the Hydrogen atom. 1) Electromagnetic Spectrum: X-rays, UV radiation, visible light, infrared, micro and radio waves. 2) Wave equation: c = λ ν, where c = m / s (speed of light), where c = wavelength (λ) frequency (ν) 3) Light from the sun: Continuous Spectrum when seen thru a prism Light from an excited element: Line Spectrum when seen thru a prism ("Emission Spectra"). 4) Light is made up of individual particle-like packets known as Photons - The energy of a photon is directly proportional to its frequency. Energy possessed by electrons in orbit can be quantized, Exists in specific quantized energy levels, and no where in between, Moves from one energy level to the next in quantum leaps in calculated orbitals. Ground State: All electrons occupy the lowest possible energy levels. Excited State: At least one electron occupies an energy level above ground state. Only certain quantum leaps are in the visible spectrum Emission Spectra vs. Absorption Spectra Emission Spectra: Electrons are excited by a form of energy (i.e. heat or electricity), and as they return to a ground state, they give off specific amounts of energy (photons of light or wavelengths) as they fall through quantized energy levels. This can be seen as distinct bands of light when viewed through a prism. Absorption Spectra: As a white light (continuous spectrum) is passed through the gas of a particular element, electrons are excited from a ground state; they absorb specific wavelengths of energy (the reverse of emission) which can be seen as distinct black lines in a continuous rainbow spectrum when viewed through a prism.

2 Woods Chem-1 Lec-04a 10-1 Elect Config (std) Page 2 Four Quantum Numbers 1) Principal (n): Energy Levels Average distance from nucleus Energy Levels 1 7: Corresponds with each row on the periodic table ("s & p" orbitals). The energy of each level is greater the further it is from the nucleus: n = 1 < n = 2 < n = 3... < n = 7 2) Sublevels (l): s, p, d, f The shape of the orbitals: at any one level, s < p < d < f Describes the shape of the orbital (From Spectroscopy: s = sharp, p = principal, d = diffuse, f = fundamental) 3) Orbitals (m l ): 1-s, 3-p, 5-d, 7-f orbitals. Where the orbital is oriented in relation to nucleus and other orbitals. s - Spherical (n = 1, 2, & 3) p - Dumbbell Shaped (2 lobes) d - Various Quaternary (4 lobes) f - (6-8 lobes)

3 Woods Chem-1 Lec-04a 10-1 Elect Config (std) Page 3 4) Electron Spin (m S ): There can only be a maximum of two electrons per orbital. Rotation or spin of an electron about its axis. It is theorized that this helps reduce the repulsion that would normally exist between electrons in the same orbital. Pauli Exclusion Principle: At any instant, an orbital may only be occupied by 0, 1, or 2 electrons. If there are more than one, they must have opposite spins (rotations). or + ½ and or ½ Hund's Rule: Each suborbital will fill in a manner to give the maximum unpaired electrons. In other words, orbitals will not get a second electron until all orbitals are half filled (one electron) ORBITALS Heisenberg Uncertainty Principle: Can't know both the position and velocity, not possible to define its exact path We can only "see" electron by it's interaction with radiation or other particles. But by doing that we disrupt its path We treat electrons not as actual particles, but as wave patterns. Orbital Shapes (Fill in electrons for H - Ne): Orbital describes where electron is 90% of the time. Electrons go into the lowest energy level available ("ground state") Ground State vs Excited State Element Electron Configuration 1s 2s 2p x 2p y 2p z 3s Orbital Shape H 1s 1 1s He 1s 2 " Li 1s 2 2s 1 1s 2s Be " B 1s 2s 2p C " N " O " Cl " Ne " Noble Gas Shorthand: Na 1s 2 2s 2 2p 6 3s 1 [Ne] 3s 1 Noble Gas Core [Ne], [Ar], etc.: Full "s" & "p" subshells. These electrons are not involved in chemical reactions Valence Electrons -- s & p: Electrons outside the Noble Gas core. Outer Octet of Electrons: ns 2 np 6» 8 electrons. Potassium thru Krypton: Overlapping Energy Levels: 4 s & 3 d» 4 s filled before 3 d» Slightly lower energy. Pseudo-Noble Gas Core: Full "d" subshell. These electrons are usually not involved in chemical reactions.

4 Woods Chem-1 Lec-04a 10-1 Elect Config (std) Page 4 Sublevel d Exceptions: K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn 4s 3d Tot:» Chromium: We would predict [Ar] 4s 2 3d 4, however» [Ar] 4s 1 3d 5 Hund's Rule: It is more energy efficient for the d orbitals to use the electron from the 4s orbital and for all d s to have one or 2 electrons than to have 2 in the s orbital and be one short in the d.» Copper / Silver / Gold: We would predict [Ar] 4s 2 3d 9, however» [Ar] 4s 1 3d 10 Simply follow the atomic numbers in the periodic table and figure out the electron configuration List the order and number of electrons in each Block (s, p, d, f): Te» [Kr] 5s 2 4d 10 5p 4 Pb» [Xe] 6s 2 4f 14 5d 10 6p 2 PROB» [Ar] 4s 2 3d 2 4p 1» What element is this? What makes it different and why? IONS: Na +» S 2» PROB» List five compounds that could have an [Ar] electron configuration. What is electron configuration for P 3-? ISOELECTRONIC: When an ion has the same electron configuration as a noble gas.

5 Woods Chem-1 Lec-04a 10-1 Elect Config (std) Page 5 Removal of Electrons to form a cation is NOT simply the reverse of filling orbitals. Electrons fill by energy orientation of orbitals» 4s before 3d Electrons removed by energy levels or shells» Level 4 before Level 3 Write down the neutral electron configuration for the element first, then add or subtract electrons to form the ion. PROB» Fe: [Ar] 4s 2 3d 6 Write Electron Configurations for the Fe 2+ & Fe 3+ ions. Calculating the Element or Ion from the electron configuration: Simply add up the number of electrons and that will tell you how many protons. If it is an ion, you simply calculate how many more or less protons there are than electrons PROB X 2+ 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 8 What is the ion? X 2 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 What is the ion? We are given the number of electrons, we must calculate protons. (you know the number of protons) The opposite of what we learned when given the element (you know the number of protons) Bohr Model» 2) 8) 8) 18) 18) 32)» Number of electrons added at each row of the Periodic Table. PROB» 2) 8) 1: What is the element? Periodic Table terminology: Rows: Energy Levels, Periods Columns: Families, Groups (e.g. Alkali Metals = Group-I, Alkali Earth Metals = Group-II, Halogens = Group-VII, Noble Gas = Group VIII) Lanthanide & Actinide Series: The two f Block rows