intro to chemistry
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Atomic Structure Nucleus- center of an atom
-contains protons
(which are positive)
-contains neutrons (which are neutral)
Ex- Sodium:
Bohr Model of Atom
Atomic Structure
Outside the Nucleus: Electrons (which are negative) surround the nucleus in energy levels
1st energy level = holds 2e
2nd energy level = holds 8e
3rd energy level = SAVE
4th energy level = FOR CHEMISTRY!!
Subatomic Particles Organized
Charge Location Mass
Protons
Neutrons
Electrons
Subatomic Particle Organized
Charge Location Mass
Protons Positive In nucleus 1 amu
Neutrons Neutral In nucleus 1 amu
Electrons Negative Outside of nucleus/ in energy levels
0 amu
Atomic Mass
An atom is defined by the number of PROTONS IT HAS!!!
Chemistry tidbits Chemical Symbol- letter representing the atom (sometimes from
Latin)
Chemistry tidbits Atomic number = number of protons
Mass number = # protons + # neutrons
Don’t bother to weigh the air inside the box
So how can you calculate NEUTRONS??
Calculating Neutrons is a simple algebraic problem…
Mass Number = protons + neutrons
Atomic Number = protons
Write the equation…
Mass Number= Atomic Number + neutrons
#Neutrons = (mass number – atomic number)
Chemistry tidbits Usually can assume:
# protons = # electrons
ONLY true for NEUTRAL ATOMS!
And remember…
Don’t mess with the
PROTONS!!!
So what CAN we “mess with?”
Neutrons…
Changes the MASS
Get an ISOTOPE
Electrons…
Changes the CHARGE
Get an ION
Atomic Mass Mystery…
Look at the atomic mass for Oxygen. What does it say (exactly?)
15.9999
What is the atomic mass?
P + N
So what the heck!?!?!
Average of the actual isotopes on Earth!!!
Isotopes
Isotopes are different atoms of the same element that contain the same number of protons but different number of neutrons.
Examples Cl-35 vs. Cl-37
17P 17P
18N 20N
How to write isotopes…
Mass/Hyphen Notation:
Especially important for a form of the isotope that is NOT the “usual”
Write the symbol, a dash, and the mass # for that isotope
Ex’s
C-14
C-12
How to write isotopes…
Nuclear Symbol Notation
Includes the symbol, atomic #, and the mass # for that isotope
Ex’s
14
6
C
What else CAN we “mess with?”
Neutrons…
Get an ISOTOPE
Electrons…
Get an ION
Periodic Table tidbits
Period table organization – organized by increasing atomic number
Split into metals (left side of stair step line) and nonmetals (right side of stair step line)
Metalloids- surround the stairstep line
Groups (families) – vertical columns (#1-18)
Periods – horizontal rows (#1-7)
Intro to Periodic Table
Periodic Table tidbits Period table organization – organized by increasing atomic number
Split into metals (left side of stair step line) and nonmetals (right side of stair step line)
ONE EXCEPTION
Hydrogen!
vertical columns (#1-18)
Groups
horizontal rows (#1-7)
Periods
Metals-left side of table
Exist as solids at room temperature
Shiny
Good conductors of heat & electricity
Malleable (can be bent)
Nonmetals-right side of table
Most are gases at room temperature
Some are brittle solids- carbon, sulfur, iodine, & phosphorus
Most do not conduct heat & electricity well
Metalloids- next to zigzag line b/w metals & nonmetals Properties fall between neighbors on both sides
Most are silvery in appearance, brittle, poor conductors of heat & electricty
Transition Metals
Metals- which are less reactive than the alkali or alkaline earth metals
Often exist as oxide or sulfide ores
ex. Iron sulfide or iron oxide
You’ll learn more in chemistry about these elements
Major Groups on periodic table
Alkali metals- group 1- most reactive Alkaline earth metals- group 2 Transition metals- groups 3-12 Metalloids- surround stairstep line Halogens- group 17 Noble gases-group 18 (inert gases-stable; nonreactive) Periodic table
Lewis Dot Structures
Lewis dot diagrams- display the number of valence electrons (outermost electrons) around the element symbol
Used to show how atoms of different elements bond and form compounds
Hint- use group number to find valence electrons
Electron configurations
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