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Subatomic Particles
Nucleus
Electrons (outside the nucleus)
= Protons + Neutrons (inside nucleus)
EX: 3 protons, 4 neutronsThe mass number = the number of protons + the number of neutrons in the nucleus
Atomic number = the number of protons in the nucleus
C126
Atomic #
Mass #
Isotopes: same # of protons, different # of neutrons
35C 37C17 17
These #'s (the 37 and the 35) are isotopes only when different. They are isotopes of each other.
35-17=18 37-17=20
CH 3 - Atomic Structure and the Periodic TableWednesday, September 12, 200712:02 AM
CHEM 1151 - Organic & Biological Chemistry.one (On 1-6-2008).one (On 6-5-2008) Page 1
Atomic weight - weighted average of the masses (in amu) of the naturally occurring isotope of an element
If total abundance is 100/5 and one is 75.77% then youmust do 100-75.77=24.23 To get the next percentage.
Let's say we have 3 isotopes
24.23%, 50.12%, (?)= 24.23 + 50.12 = 74.35 = 100 -74.35 = 25.65
* Note: amu will always be given
25.65 is the next percentage of the sequence
Pg 52, Practice 3.2
69.09 x 62.93 + 30.91 x 64.93100 100
= 63.5543.4783 + 20.0699=63.5482
Mass and Size of an Atom
Lead - 208 # of protons + # of neutrons 82 protons + 126 Neutrons = 208 (208 is the mass #)
EX: if I have 7 protons then I have 7 electronsProtons and electrons are equal
Periodic Chart (starts on slide 3-8)
CHEM 1151 - Organic & Biological Chemistry.one (On 1-6-2008).one (On 6-5-2008) Page 2
Periodic Chart (starts on slide 3-8)
H1
1.01
Atomic #
Atomic Weight / Mass
All the horizontal rows in the chart are called periods
We will follow old notation in class, the IA, IIA, IIA and etc. not Group 1, 2, 3, 4 and etc.EX: Al is in period 3 Group IIIA
All the vertical rows in the chart are called groups
Metals - solid at room temperature (except for Hg, which is a liquid), shiny, conduct electricity and are ductile and malleable
Nonmetals
Except for graphite, do not conduct electricity-
In chemical reactions, they tend to accept electrons (Slide 3-11)-
- Except for hydrogen, lie on the right side of the periodic chart
Electrons - 1
L1 --> L+
L2 --> L++
O -------------- O-
+2eO -------------- O-2
+eThe minus sign can be eitherIn the front or back
Group IA are elementsGroup 8A are elementsGroup IIA are alkaline Earth MetalGroup VIIIA are noble Gases
(Slide 3 - 17)The middle group are transition elements
Metalloids - have some properties of metals and nonmetals
We should be able to tell which group an element is in. We do not need to memorize the chart, it Will be provided. It would be good to know the first 20 elements (they are the most popular)
Ground State Electron Configuration = most stableElectron Configuration (Slide 3-16)
N = 1 = 2 * 1^2 = 2 N = 2 = 2 * 2^2 = 8 N = 3 = 2 * 3^2 = 18 N = 4 = 2 * 4^2 = 32
The number 1,2,3,4 are the shell numbers
CHEM 1151 - Organic & Biological Chemistry.one (On 1-6-2008).one (On 6-5-2008) Page 3
See Slides 3-18 through 3-22. To get a better understanding on the order of the 1s, 2s, 2p, 3s sequence see the chart on page 64 in the book. Also look and the Orbital Diagrams that go along with it on pages 62-65
1st shell has 1 orbital2nd shell has 2 orbital's3rd shell has 3 orbital's4th shell has 4 orbital's
When you look at the orbital boxes on those pages remember that you always draw the boxes first, then you fill in the up arrows then you go back to the first box if needed and fill in the down arrows.
For example: let's say you have5 boxes to fill out you fill out the Up arrows first, then you fill out the Down arrows. Sorry, but I'm not Gonna draw a whole bunch of boxesAnd arrows, that just takes too muchI'll show you my notes, but the bookHas a good amount of them.
This is where we left off. After that all she said was to do the in chapter and out of chapter questions in the book. Also for us to make sure we keep an eye on webct because she will be posting things on there for us such as homework, assignments and etc.
Orbital Diagrams give a more complete indication of the electron quantum numbers. Each
CHEM 1151 - Organic & Biological Chemistry.one (On 1-6-2008).one (On 6-5-2008) Page 4
Orbital Diagrams give a more complete indication of the electron quantum numbers. Each orbital represented by a box and each electron by a half -arrow.
For example Hydrogen has 1 electron. That electron goes into the lowest energy orbital, that is the 1s orbital. Thus we write...
For Boron we start with 5 electrons. Again we start by filling the lowest energy orbital 1s, then the 2s orbital, and finally putting one electron in the 2p orbital...
Hund's Rules: Electrons occupy different orbital or a given subshell with spins in the same direction before spin pairing occurs.
Now let's look at Carbon, which has 6 electrons.
Therefore for carbon we have
Another example, Neon has 10 electrons.
For Neon, both the n=1 and n=2 shells are completely full.Let's look at Sodium, which has 11 electrons.
Na has one electron its outermost shell. For convenience we often represent the electron configuration of the closed shells with the corresponding noble gas symbol. So for sodium we would write:
CHEM 1151 - Organic & Biological Chemistry.one (On 1-6-2008).one (On 6-5-2008) Page 5
tutorials, organic and biological chemistry, orbital diagrams - Google Search
http://www.google.com/search?q=tutorials,+organic+and+biological+chemistry,+orbital+diagrams&hl=en&rlz=
1T4GZAZ_enUS228US228&start=20&sa=NScreen clipping taken: 9/9/2007, 8:29 PM
[Ne] 3 s1 where [Ne] represents 1s2 2s2 2p6
In fact we distinguish between electrons depending on whether they part of the closed shell or in the outermost shell.
Valence Electrons: Electrons in the outermost shell (principal quantum level) of an atom. •Core Electrons: Electrons in the inner closed shells. •
If you look at the periodic table you will notice that elements in the same group have the same number of valence electrons. That is the main reason why elements in the same group have such similar chemical and physical properties.
Let's look at Argon, which has 18 electrons. It has the configuration1s2 2s2 2p6 3s2 3p6
Pasted from <http://www.grandinetti.org/Teaching/Chem121/Lectures/MultiElectronAtoms/ >
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