Two rockets are each 1000 m long in their rest frame. Rocket Orion, traveling at 0.80c relative to the earth, is overtaking rocket Sirius, which is poking along at a mere 0.60c. According to the crew on Sirius, how long does Orion take to completely pass? That is, how long is it from the instant the nose of Orion is at the tail of Sirius until the tail of Orion is at the nose of Sirius?
February 1519 Chapter 3 Notes (Continued): Atoms and Ionic Bonds: *Removing Valence electrons to form a cation requires the INPUT of energy* Ionization Energy: - Lowest ionization energy for group 1A cations because they have low effective nuclear charge and large radii - Ionization Energy increases up and to the right of the periodic table Ionization Radii: - Beryllium: [He]2S 2 2 1 - Boron: [He]2S 2P - Magnesium: [Ne]3S 2 2 1 - Aluminum: [Ne]3S 3P - Easier to remove electrons from p subshell than a full s subshell 1 3 - Nitrogen: [He]2S 2P - Oxygen: [He]2S 2P 1 4 - Easier to remove a paired p electron than to remove a p electron from a half full subshell Higher Ionization Energy: st - 1 ionization energy: +energy m+ + e o Mg: 1S 2S 2P 3S Mg : 1S 2S 2P 3S 2 2 6 1 nd + 2 - 2 ionization energy: m + Energy m + +e o Mg : 1S 2S 2P 3S Mg : 1S 2S 2P+2 2 2 6 rd +2 3+ - 3 ionization energy: m + Energy m + e o Mg : 1S 2S 2P Mg : 1S 2S 2P3+ 2 2 5 VERY UNLIKELY! Requires too much energy!!! So, Magnesium has the highest 3 ionization energy Electron Affinity: - Energy released when adding electrons is favorable - Greatest electron affinity for the halogens - Least electron affinity for group 2A, 5A, and Noble Gases - Electron Affinity increases up and to the right on the periodic table Octet Rule: - Main group elements undergo reactions that give them 8 valence electrons (full s and p subshells) – same as noble gases - An element with 8 valence electrons are unlikely to undergo further reactions o EXCEPTIONS: H, Li, and Be undergo reactions that give them 2 valence electrons (same as He) Ionization Energy: - 1A Elements: Lose one electron - 2A Elements: Lose two electrons Electron Affinity: - 6A Elements: Gains two electrons - 7A Elements: Gains one electron - 8A Elements: unlikely to gain/lose electrons BornHaber: (Will not be tested on this nor will it be on the homework) + Na + Cl Na + Cl Na: 1S 2S 2P 3S 6 1 Na : 1S 2S 2P 2 6 2 2 6 2 5 2 2 6 2 6 Cl: 1S 2S 2P 3S 3P Cl: 1S 2S 2P 3S 3P E ior Na = +495.8 kJ/Mol Unfavorable (requires energy) E for Cl = 348.6 kJ/Mol Favorable (releases energy) EA Change in Energy = +147.2 kJ/Mol - Ionic compounds are very stable - Requires more steps than previously seen 1) Na(s) Na(g) 2) ½ Cl (g2 Cl(g) + 3) Na(g) Na (g) + e a. 495.8 kJ/Mol 4) Cl(g) + e Cl(g) a. 348.6 kJ/Mol + 5) Na (g) + Cl(g) NaCl(s) a. 787 kJ/Mol *Most favorable step LATTIC ENERGY* Lattice Energy: - Reflects the strength of an ionic bond - Energy = to the lattice energy is released when gaseous ions form the compound - Breaking apart an ionic compound requires energy input equivalent to lattice energy Lattice Energy Depends on: 1) Magnitude (Greater charge, greater Lattice Energy) 2) Size of ion (Greater size, smaller the Lattice Energy) Alkali Metal Chemistry (1A): 1 - Valence shell electron configuration: ns - M m + 1e - 2m(s) + 2H O(l2 2m OH(aq)2+ H (g) 2 - 4m(s) + O (g)2 2m O(s) 2 - Loses electrons very readily *strong reduction agents* o 4Li(s) + O (g) 2 2Li O(s) 2Anion O is oxide2 2 o 2Na(s) + O (g) 2Na O (s) 22Anion O is peroxid2 o K(s) + O (g) 2 KO (s) 2 Anion O is super2xide + - M(s) m (solution) + 1electron(solution) (solvated electrons in liquid ammonium AlkalineEarth Metals (2A): - Valence shell electron configuration: ns 2 2+ - M m + 2electrons - Be(s) + 2H O(l2 No reaction - Mg(s) + 2H O(l2 Mg(OH) (aq) + H2(g) Slow R2action - Ca(s) + 2H O(l2 Ca(OH) (aq) + 2 (g) Fast 2eaction (also happens with Sr and Ba) Halogens (7A): - X + 1Electron X (X usually represents Halogens) - Gains electrons very readily *strong oxidizing agents* - X 2g) + H (g2 2HX(g) - HX = Hydrogen halide = acide - nX (2) + 2m(s) mX (s) n - mX n Metal Halide Noble Gases (8A): - Colorless, odorless, (mostly!) nonreactive gases - Ar, Ke, and Xe only react with Fluorine - First Noble Gas compound, Xe [ptF ], made by Neil Bartlet in 1962 6 Chapter 4: Chemical Bonds: Ionic Bonds: Transferred electrons between atoms (bound by +/ attreactions) Covalent Bonds: Nonmetal and nonmetal bond by sharing electrons (bound by shared electron cloud) Property: NaCl: HCl: Appearance: White Solid Colorless Gas Type of Bond: Ionic Covalent Melting Point: 801 C 115 C Boiling Point: 1465 C 84.9 C - Solids have low energy gas phase has the most energy - Balance of attractive and repulsive forces - Nucleus and electron forces participate in bonding Representing Molecules: - Chemical Formula: C H O2 6 - Structural Formula: - Molecular Model: