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Atoms, Isotopes and Ions…Oh My!SOL Covered:
PS.3, PS.4a & bCH.2 a, b, c, g & i
Aron [email protected]
Objectives
• Review the history of Atomic Theory
• Emphasize the importance of the Quantum Model
• Build atomic models with appropriate atomic mass and electron configuration
• Build models to represent ionic and covalent bonding
A Brief History of the Atom
What is Matter Made of? Aristotle vs. Democritus
(Around 2400 years ago)
What is Matter Made of? Aristotle vs. Democritus
(Around 2400 years ago)
John Dalton
Dalton’s Theory Based on Experimentation!
• chemical elements are made of atoms. • the atoms of an element are identical in
their masses• atoms of different elements have different
masses • atoms only combine in small, whole
number ratios• atoms can be neither created nor
destroyed
Dalton’s Atomic Model
J.J. Thomson
Ernest Rutherford
BOTTOM LINE- The nucleus is dense and positive and the atom is mostly empty space!
Atoms are Mostly Empty Space
Imagine a raisin on home plate to represent the nucleus
The first electron would be represented by the outfield wall.
Niels Bohr
• Rutherford quickly realized that his model would cause the electrons to be pulled into the nucleus and destroy the atom
• In 1913, Niels Bohr hypothesized that the electrons were in fixed energy levels at a set distance from the nucleus and that each energy level could hold a certain number of electrons.
Bohr Model Continued
• Energy levels are sometimes called “shells”
• Each shell can hold a fixed number of electrons
• Electrons are particles but the position and velocity can not be determined at the same time– Heisenberg
Uncertainty Principal
The Quantum ModelThe “Modern” Model
• In the early 1920’s, and Irwin Schrödinger theorized that the electrons behaved like particles and waves. His model kept electrons energy levels and the energy levels were broken into sub-levels.
• The energy levels aren’t traditional “orbital's” but areas where an electron has a high probability of being found.
Quantum Orbital's Have Interesting Shapes
The Quantum Model is also known as The Electron Cloud
Even though the Quantum/Electron Cloud Model is the most accurate, the Bohr Model
is still used to help students understand atomic structure since it’s simplistic.
Correct- Quantum Model/Electron Cloud
Bohr’s model while not completely accurate, helps students understand energy levels and placement of electrons.
So what’s the difference between protons, neutrons and electrons?
Let’s Build Some Models!
Hydrogen-1
Make an atom for…
Hydrogen-2
Make an atom for…
So what’s the difference between…
and
has 1 more neutron
and are _______ of HydrogenISOTOPES
Helium-4
Make an atom for…
Make an atom for…
Make an atom for…
Make an atom for…
Nitrogen-17
Make an atom for…
Let’s Take a Break and Play a Game
• Slowly move around the designated area looking down
• When you bump into someone, share your number– The lower number will give 1 bean to the
higher number
• Continue until I call stop
Now let’s make some Ions…
Make an atom for…
2-
Atoms with a NEGATIVE net charge are called ANIONS
2-
Make an atom for…
1+
Atoms with a POSITVE net charge are called CATIONS
Ionic BondingChemical Bonds Between Metals and Nonmetals
Sodium and Chlorine
Na11 electrons
Cl17 electrons
Sodium and Chlorine
Na1+
10 electrons
Cl1-
18 electrons
Electron from Na
8 electrons in each outer energy level
Sodium chloride
NaCl
Opposites attract!
Calcium and Chlorine
Ca ClCalcium has 2 electrons in it’s outer energy level
Calcium and Chlorine
Ca2+ 2Cl1-
Calcium donates one electron to 2 Chlorine atoms
Calcium chloride
CaCl2
Covalent BondingChemical bonds between two or more nonmetals
Hydrogen and Oxygen
2H O
Water
H2O
Water
Each Hydrogen atom has two electrons- the maximum number in the first (and only for Hydrogen) energy level
Water
The Chlorine atom has 8 electrons in the second energy level which is the maximum number of electrons that the second energy level can hold.
Ammonia (nitrogen trihydride)NH3
Nitrogen atom
3 Hydrogen atoms
Ammonia (nitrogen trihydride)NH3
Ammonia (nitrogen trihydride)NH3
Each Hydrogen has 2 electrons which is the maximum it can hold in it’s outer energy level.
Ammonia (nitrogen trihydride)NH3
Nitrogen has 8 electrons in it’s outer energy level which is the maximum number of electrons the second energy level can hold.
Methane (carbon tetrahydride)CH4 For chemistry, you can use this
to talk about sp hybridization (specifically sp3)