Lecture 9 - T opics for the day Administrative stuff Exam...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Topics for the day Administrative stuff Exam One Where were we? Electronegativity Dipole moments Lattice energy Predicting ionic compounds Administrative stuff Exam grading questions. Email me your request. Documentation for permission to makeup any of the other in- class exams due to class conflicts must be sent to me by 5 pm today. Homework will be posted later today (switching to Tues HW so you have it before the next exam) For the question asking why different elements have different line spectra: “Because they have different orbital energies” is the best answer. But two other answers — “different number of protons” and “different number of electrons” — are also correct. For this reason I am giving everyone the 8 points for that question; i.e., everyone gets it correct. Exam One
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
For those of you who actually did give the best answer Yes, giving everyone else those 8 points, means that everyone else increases their score by 8/300 points = 2.7% Yes this does raise the class average Yes this does mean that your position relative to the class average has now dropped. BUT I don’t curve, so your position relative to the class DOESN’T MAKE ANY DIFFERENCE to your grade. CH301: Regraded Exam 1 0 5 10 15 20 25 30 35 40 45 0 10 20 30 40 50 60 70 80 90 % score Number of students Class Average 75% X-axis is clearer. Two more exam grades added. One question credited to all. A B C D F A 19% B 22% C 27% D 15% F 17% Bond Energy Attraction Repulsion Stable molecule Bond Length The H 2 molecule forms at the position that gives the lowest possible energy, balancing the negative attraction and the positive repulsion. This position is the equilibrium internuclear distance, or bond length . Last Time The bond is formed because the H 2 molecule is more stable (i.e., lower energy) than two separated hydrogen atoms. The amount by which it is more stable is known as the bond energy
Background image of page 2
Cl Na + Ionic bonds electron transfer Covalent bonds electrons shared equally The description of a covalent bond showed equal sharing of electrons between two identical atoms (in this case hydrogens) to form a homonuclear molecule. More often, a covalent bond is between two different atoms, and one or the other of the two atoms will attract the electrons more strongly. We need to be able to quantify this electron attraction.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/18/2009 for the course CH 52375 taught by Professor Ruth during the Spring '09 term at University of Texas.

Page1 / 11

Lecture 9 - T opics for the day Administrative stuff Exam...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online