Quiz results and the begining of bonding and molecular structure

For Students:
The quiz results are as follows:
1.  Chromium = 1s2 2s2 2p6 3s2 3p6 3d5 4s1
2.  What is the maximum number of electrons that can be identified with each of the following sets of quantum numbers?
a.  n = 4, l = 3 ml = 1 1/2? --> 2
b.  n = 6, l = 1, ml = -1, ms = -1/2  --> 1
c.  n = 3, l = 3, ml = -3  -->  none because l cannot equal n

3.  Arrange the following atoms in order of increasing ionization energy: Si, K, P, and Ca
K < Ca < Si < P

The picture shown above is called a Lewis dot structure.  These are for CH4, C2H4 and C2H2.  Structure refers to the way atoms are arranged in space, and bonding describes the forces that hold adjacent atoms together.  When a chemical reaction occurs between two atoms, their valence electrons are reorganized so that a net attractive force - a chemical bond - occurs between atoms.  There are two general types of bonds.  Ionic bonds form when one or more valence electrons are transferred from one atom to another, creating positive and negative ions.   In contrast, a covalent bond involves sharing of valence electrons between atoms.

The american chemist Gilbert Newton Lewis introduced a useful way to represent electrons in the valence shell of an atom.  The element's symbol represents the atomic nucleus together with the core electrons.  Up to four valence electrons, represented by dots, are placed one at a time around the symbol; then, if any valence electrons remain, they are paired with ones already there.  These pictures are refered to as Lewis electron dot symbols, and the pictures above are great examples!

For Parents:

The exam last week went very well.  The average grade was a B-, which is quite good!  If your child did not receive the grade they wanted or if there is something they don't understand, please have them come and see me.  Thanks again for all you do!