Unit 4.2 Notes.doc
4.2 & 3 DEFINITIONS & NOTES – ATOMIC STRUCTURE Particle
Location
Electron Proton Neutron
Outside Nucleus Inside Nucleus Inside Nucleus
Symbol
Relative Charge
e-
-1 or 1-
p+
+1 or 1+
0 or n
0
Relative Mass Mass (proton = 1) Analogy 1 Pickle ≈ (very small mass) 2000 Watermelon 1 (large mass) 1
Text book
NUCLEUS – the central part of the atom. It contains the protons and neutrons. ELECTRONS – negatively charged particles circling the nucleus. They have very little mass. PROTONS – positively charged particles in the nucleus. The number of protons determines the element. NEUTRONS – particles with no charge in the nucleus. They help create stability. The glue of the nucleus. ATOMIC NUMBER – The number of protons in the nucleus. The whole number on the periodic table.(Integer) 1,2,3….. ATOMIC MASS – mass of a single atom of an element, measured in atomic mass units. The ATOMIC MASS IS THE number including a decimal on the periodic table.
ATOMIC MASS UNIT – the mass of a single atom of H, abbreviated amu ISOTOPES – atoms of an element with varying numbers of neutrons in nucleus ENERGY LEVEL – possible quantities of energy can possess, This is like a stair case ORBITAL –spatial regions around the nucleus of the atom where an electron is likely to be found. EXAMPLE: Atomic Symbol
8
O 15.9994
Atomic Number – Number of protons in nucleus Atomic Mass – Mass of a single (average) atom in Atomic Mass Units.
Why is the Atomic Mass of H not 1? Different number of neutrons creates isotopes
How do electrons circle the Nucleus? What is the pattern of electrons around the nucleus? How can a sketch of the atom be made from Periodic Table Information? Electrons fill inner shells first.
What is the Atomic# ? The number of protons and electrons (neutral atom). Atomic # = p = e (Neutral Atom)
What is a row (Period) in the Periodic Table? The row an element is in tells how many shells the atom will have. Row = Shells
The number or elements in a row also tells the number of electrons each shell can hold. # of Electrons in Period elements in Period 1 2 1st shell = 2 2 8 2nd shell = 8 3 8 3rd shell = 8
What is a column (Group) in the Periodic Table? The tall groups numbered with the letter A give the number of electrons in the outer shell. Outer shell electrons are called “Valence Electrons”. Group = Outer Shell Electrons = Valence Electrons
Summary of Rules Electrons fill inner shells first. Atomic # = p = e (Neutral Atom) Row = Shells Group = Outer Shell Electrons = Valence Electrons
Try Drawing Carbon for Example Electrons fill inner shells first. Atomic # = p = e (Neutral Atom)
Carbon is Atomic #6, so it has 6 protons and 6 electrons in the outer shell.
Row = Shells
Carbon is in the 2nd Row, so it will have 2 shells.
Group = Outer Shell Electrons = Valence Electrons
Carbon is in the 4th Group, so it will have 4 valence electrons (outer shell electrons) .
Example:
Carbon ELECTRON CONFIGURATION A list of the number of electrons in each shell. For Carbon 2,4
1st shell has 2 e, 2nd shell has 4 e
DRAW THE STRUCTURE OF SULPHUR AND WRITE THE ELECTRON CONFIGURATION Electrons fill inner shells first. Atomic # = p = e (Neutral Atom) Row = Shells Group = Outer Shell Electrons = Valence Electrons
CONFIGURATION: _____ , _____ , ______
ISOTOPES MASS NUMBER = # OF PROTONS + # OF NEUTRONS MASS NUMBER –
sum of the protons and neutrons in the nucleus used for designating the different isotopes not listed in periodic table because # of neutrons varies in Isotopes NUCLEAR SYMBOL
General Form
Mass# Atomic #
HYPHEN NOTATION General Form
X
Example
X – Mass # Example
C – 13
13 6
C
Read “13, 6 Carbon”
Read “Carbon 13”
Three Isotopes of Carbon are known:
12 6
13 6
C
14 6
C
C
How many neutrons does each Isotope of Carbon have? Fill in the missing information. Nuclear Symbol
# of protons
# of neutrons
# of electrons
Electron Configuration
22 17
Cl
17
5
17
2,8,7
6 4
Be
4
2
4
2,2
20
8
20
2,8,8,2
16
11
16
5
2,8,8
DOT NOTATION or LEWIS STRUCTURE – symbol with the number of valence electrons DEFINITION: VALENCE ELECTRONS - the outer orbit electrons, it is these electrons that determine the way in which the element acts These are shown as dots surrounding the chemical symbol. Draw dots on the sides (left, right, top and bottom) of the symbol Start on top and place a dot on top and work clockwise around the symbol as shown below THESE ARE THE OUTER SHELL ELECTRONS ONLY
1 5
8 4
X
2 6
3 7
EXAMPLE:
I
P
Ca
C
Ne
Si
4.2 NOTES ON CALCULATING AVERAGE ATOMIC MASS Working from Mass Number & % Abundance to get Atomic Mass Information on % and mass of each Isotope will be given similar to the table shown to the left.
Convert the % to a decimal (if it is not already a decimal)
75.77 % .7577 24.23 % .2423
Multiply the Mass Number by the Corresponding % Abundance 35 x .7577 = 26.5195 AMU 37 x .2423 = 8.9651 AMU
Add the results 26.5195 AMU + 8.9651 AMU = 35.485 AMU (Rounded answer)
Isotope
Multiply Across % Abundance Mass (AMU)
Subtotal (AMU)
Cl-35
.7577
35
26.5195
Cl-37
.2423
37
8.9651
Total -
35.485
Add Down
TRY THE SAME WORK SETTING UP A TABLE AS SHOWN HERE
Working from “Exact Weight” & % Abundance to get Atomic Mass Information on % and mass of each Isotope will be given similar to the table shown to the left.
Convert the % to a decimal (if it is not already a decimal)
75.77 % .7577 24.23 % .2423
Multiply the Mass Number by the Corresponding % Abundance 34.968852 x .7577 = 26.42596 AMU 36.965903 x .2423 = 8.956838 AMU Add the results
26.42596 AMU + 8.956838 AMU = 35.3828 AMU (Rounded answer)
Isotope
Multiply Across % Abundance Mass (AMU)
Subtotal (AMU)
Cl-35
.7577
34.968852
26.42596
Cl-37
.2423
36.965903
8.956838
Total -
35.3828
Add Down
TRY THE SAME WORK SETTING UP A TABLE AS SHOWN HERE
Internet Resources: http://www.chemteam.info/Mole/AverageAtomicWeight.html https://d3jc3ahdjad7x7.cloudfront.net/fxGaDQWE1TSPqzJxM9go75zFU2vngGfk7IwXnzmsXFBgnc 0d.pdf
