Quantum theory predicts that an atom s electrons are found in: To account that orbitals hold two electrons, we need:

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Benedict Foster
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1 Quantum theory predicts that an atom s electrons are found in: To account that orbitals hold two electrons, we need: Shells (principle quantum number, n) Subshells (angular momentum, l) Orbitals (magnetic quantum number, m l) We will examine those predictions Spin quantum number, ms= +½ or ½) ms= +½ represents one electron, and ms= ½ represents the other. Scientists verified electron spin experimentally Electron spin affects magnetic properties Four quantum numbers account for all electrons in atoms: Diamagnetic: not attracted to magnetic field Paramagnetic: attracted to magnetic field Substances with unpaired electrons are paramagnetic n=, 2, 3, 4,... (integers) l= 0 to n- (integers) m l= l to l (integers) ms = +½, ½ Pauli Exclusion Principle No two electrons can have the same quantum numbers. For a orbital with 2 electrons, if electron has quantum numbers of n=0, l=0, m l =0 and ms= +½, the other electron has n=0, l=0, m l =0 and ms= ½. Electrons have unique addresses. Electron placement in atoms The n= shell has 2 electrons, both in a orbital. The n=2 shell has 8 electrons, 2 in a orbital, and 6 in three orbitals. The n=3 shell has 8 electrons, 2 in a orbital, 6 in three 3p orbitals, and 0 in five orbitals. The n=4 shell has 32 electrons, 2 in a orbital, 6 in three 4p orbitals, 0 in five 4d orbitals, and 4 in seven 4f orbitals.

2 Energy Aufbau Principle gives filling order for electrons in orbitals in atoms 7s 6s 5s 7p 6p 5p 4p 3p 6d 5d 4d 5f 4f...or use the periodic table Write electron configurations using notation Example: an electron configuration (EC) of 2 means 2 electrons in the orbital. It would refer to helium in the ground state. Example: an EC of means electron in the orbital. It refers to hydrogen in the ground state. For the ground state EC, fill one type of orbital before starting the next. More EC Examples Write the EC of Li. Answer: 2. Write the EC of B. Answer: 2 2. Write the EC of C. Answer: Write the EC of Na Write the EC of Ar p 6. Write the EC of Fe p Write EC using and orbital box notation Orbital box notation Element H He Be Which would be paramagnetic and diamagnetic B C N O Hund s Rule Place electrons singly and with spins aligned within orbitals of the same energy. Write the orbital box notation for carbon, nitrogen, oxygen, fluorine, and neon F Ne The or orbital box shorthand notation starts from the previous noble gas. Write the EC for Na and Ca in shorthand orbital box and notation. Orbital box Na [Ne] Na [Ne] Ca [Ar] Ca [Ar] 2

3 / Charg Atomic number (Z) Predicted electron configuration. Dashed lines indicate exceptions p 4 3p2 5 3p3 6 3p4 7 3p5 8 3p6 (223) (226) (227) (26) (262) (266) (264) (277) (268) (27) (272) (278) (284) (289) (288) (292) 58 4f 59 4f2 60 4f3 6 4f4 62 4f5 63 4f6 64 4f7 65 4f8 66 4f9 67 4f0 68 4f 69 4f2 70 4f3 7 4f (45) f 9 5f2 92 5f3 93 5f4 94 5f5 95 5f6 96 5f7 97 5f8 98 5f9 99 5f0 00 5f 0 5f2 02 5f3 03 5f (237) (244) (243) (247) (247) (25) (252) (257) (258) P Write the EC for P and Fe and Se in shorthand orbital box and notation. Orbital box [Ne] 3p P [Ne] 2 3p 3 Fe [Ar] Fe [Ar] 2 6 Se [Ar] Se [Ar] 2 0 4p 4 4p Write the EC for La, Ce, Th, and U in shorthand notation (see periodic table). notation La [Xe]6s 2 5d Ce [Xe]6s 2 5d 4f Th [Rn]7s 2 6d 5f U [Rn]7s 2 6d 5f 3 To get the EC of an ion, remove electrons from shell with the highest n first. For example, form + and +3 ions of Ga [Ar] 2 0 4p Ga + [Ar] 2 0 Ga+3 [Ar] 0 Electrons come from n=4 before n=3, p subshells empty before s subshells. Form +3, +5, and -3 ions of N [He]2 3 N+3 [Ne] 2 N+5 [He] N 3 [He] 2 6 A half filled subshell has a special stability. Form +2 and +4 ions of Co [Ar] 2 7 Co +2 [Ar] 7 Co +4 [Ar] 5 Is Co+4 paramagnetic or diamagnetic? Draw the orbital box diagram. Co +4 is paramagnetic with 5 unpaired electrons. The ion has a special stability from a half-filled d subshell. Co [Ar] Predictions about magnetic properties need the orbitals that came from the quantum mechanics model. Atomic size Ion size Electron affinity Periodic Trends by orbitals experiencing higher thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium Summer 20

4 / Charg Atomic number (Z) Predicted electron configuration. Dashed lines indicate exceptions p 4 3p2 5 3p3 6 3p4 7 3p5 8 3p6 (223) (226) (227) (26) (262) (266) (264) (277) (268) (27) (272) (278) (284) (289) (288) (292) 58 4f 59 4f2 60 4f3 6 4f4 62 4f5 63 4f6 64 4f7 65 4f8 66 4f9 67 4f0 68 4f 69 4f2 70 4f3 7 4f (45) f 9 5f2 92 5f3 93 5f4 94 5f5 95 5f6 96 5f7 97 5f8 98 5f9 99 5f0 00 5f 0 5f2 02 5f3 03 5f (237) (244) (243) (247) (247) (25) (252) (257) (258) / Charg Atomic number (Z) Predicted electron configuration. Dashed lines indicate exceptions p 4 3p2 5 3p3 6 3p4 7 3p5 8 3p6 (223) (226) (227) (26) (262) (266) (264) (277) (268) (27) (272) (278) (284) (289) (288) (292) 58 4f 59 4f2 60 4f3 6 4f4 62 4f5 63 4f6 64 4f7 65 4f8 66 4f9 67 4f0 68 4f 69 4f2 70 4f3 7 4f (45) f 9 5f2 92 5f3 93 5f4 94 5f5 95 5f6 96 5f7 97 5f8 98 5f9 99 5f0 00 5f 0 5f2 02 5f3 03 5f (237) (244) (243) (247) (247) (25) (252) (257) (258) / Charge Atomic number (Z) Predicted electron configuration. Dashed lines indicate exceptions. 2 2 H Normal font=solid, outline=liquid, italic=gas at room temperature He lithium beryllium boron carbon nitrogen oxygen fluorine neon p 4 3p2 5 3p3 6 3p4 7 3p5 8 3p6 (223) (226) (227) (26) (262) (266) (264) (277) (268) (27) (272) (278) (284) (289) (288) 58 4f 59 4f2 60 4f3 6 4f4 62 4f5 63 4f6 64 4f7 65 4f8 66 4f9 67 4f0 68 4f 69 4f2 70 4f3 7 4f (45) f 9 5f2 92 5f3 93 5f4 94 5f5 95 5f6 96 5f7 97 5f8 98 5f9 99 5f0 00 5f 0 5f2 02 5f3 03 5f (237) (244) (243) (247) (247) (25) (252) (257) (258) (292) Shielding of charge from nucleus by electrons A noble gas EC is very effective at shielding the charge from the nucleus to outside the atom because all of the orbital space is filled by electrons. An incomplete EC is less effective at shielding charge from the nucleus because the orbital space is not filled. Nuclear charge experienced outside the atom increases as we move to the right on the periodic table because nuclear charge is poorly shielded by an incomplete EC. Atomic Size Atomic size increases when electrons are less tightly held. Atomic size increases Fr is the largest atom. by orbitals experiencing higher thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium Summer 20 Atomic size increases Ion Size Cations are smaller than the atoms from which they come because there is an excess of positive nuclear charge that pulls more strongly on the remaining negatively charged electrons, shrinking the cation. Anions are larger than the atoms from which they come because the excess of negative charge from the electrons causes repulsion, so the anion grows in size. is the energy needed to remove an electron from the gas phase atom. He has the largest ionization energy thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium Summer 20 Ionization Energy The first ionization energy of Mg is about 740kJ, Mg Mg + + e The second ionization energy of Mg is about 500kJ, Mg + Mg +2 + e The third ionization energy of Mg is about 7800kJ, Mg +2 Mg +3 + e Breaking a filled subshell requires a large amount of energy 7.8MJ, so this chemistry does not happen unless high energy is used. Metals lose electrons (good reducing agents) more easily than non (good oxidizing agents). Metals lower in a group are better reducing agents, while non (other than noble gases) higher in a group are better oxidizing agents. thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium Summer 20

5 / Charg Atomic number (Z) Predicted electron configuration. Dashed lines indicate exceptions p 4 3p2 5 3p3 6 3p4 7 3p5 8 3p6 (223) (226) (227) (26) (262) (266) (264) (277) (268) (27) (272) (278) (284) (289) (288) (292) 58 4f 59 4f2 60 4f3 6 4f4 62 4f5 63 4f6 64 4f7 65 4f8 66 4f9 67 4f0 68 4f 69 4f2 70 4f3 7 4f (45) f 9 5f2 92 5f3 93 5f4 94 5f5 95 5f6 96 5f7 97 5f8 98 5f9 99 5f0 00 5f 0 5f2 02 5f3 03 5f (237) (244) (243) (247) (247) (25) (252) (257) (258) Electron Affinity Electron affinity is the energy released when adding an electron to a gas phase atom. Electron affinity increases F has the largest electron affinity thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium Summer 20 Electron affinity increases Electron Affinity Noble gases have no affinity for electrons. Oxygen has an affinity for electrons but nitrogen does not. Use use the orbital box notation to explain why this might be so. N O Nitrogen enjoys the special stability of a half-filled subshell, so it does not easily take another electron (it would require electron pairing). Oxygen takes electrons because electrons experience a strong nuclear charge.

Chapter 7 The Structure of Atoms and Periodic Trends

Chapter 7 The Structure of Atoms and Periodic Trends Jeffrey Mack California State University, Sacramento Arrangement of Electrons in Atoms Electrons in atoms are arranged as SHELLS (n) SUBSHELLS (l) ORBITALS