1. Chapter 4 Atomic Structure 4.2 Structure of the Nuclear Atom
4.1 Defining the Atom
4.2 Structure of the Nuclear
Atom
4.3 Distinguishing Among Atoms
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2. Early Models of the Atom
Do Now
Take out your Study Guide
What questions do you have for tomorrow’s test?
Read the lab (on front table).
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3. Early Models of the Atom
Dalton
English chemist & school teacher
(1766 – 1864)
Used experimental methods to develop scientific theory
Democritus
Greek philosopher (460 BC –370 BC)
Reasoned atoms were indivisible & indestructible
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4. Early Models of the Atom
Dalton’s Atomic Theory – True or False?
Elements are composed of tiny indivisible atoms.
Atoms of the same element are identical. Atoms of one element differ from those of another element.
Atoms of different elements can physically mix or chemically combine in simple whole-number ratios to form compounds.
Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element are never changed into atoms of another element as a result of a chemical reaction.
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5. In 1897, J. J. Thomson discovered the electron.
Subatomic Particles
Electrons
In 1897, J. J. Thomson discovered the electron.
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6. Thomson’s atomic model
Plum Pudding Model
Thomson’s atomic model
Electrons stuck in a lump of positive charge, similar to raisins stuck in dough.
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7. Rutherford’s Gold-Foil Experiment
The Atomic Nucleus
Rutherford’s Gold-Foil Experiment
Beam of alpha
particles directed at
sheet of gold foil.
Some particles
bounced off of
gold foil.
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8. The Rutherford Atomic Model Protons and neutrons are in the nucleus
The Atomic Nucleus
The Rutherford Atomic Model
Protons and neutrons are in the nucleus
Electrons around nucleus occupy almost all of the volume of the atom
Did NOT explain chemical properties of elements
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9. Key Concepts
If an atom were the size of a football stadium, the nucleus would be the size of a marble
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10. Energy Levels in Atoms
The Bohr Model
Each possible electron orbit has a fixed energy known as an energy level.
Quantum of Energy
Amount of energy required to move an electron from one energy level to another.
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11. Each energy level can hold a specific number of electrons.
Energy Levels in Atoms
Each energy level can hold a specific number of electrons.
Maximum # electrons = 2n2
Energy Level
(n)
Max #
Electrons 1 2 8 3 18 4 32
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12. It is the same number as the period (row) on periodic table
Atomic Orbitals
Energy Level (n)
It is the same number as the period (row) on periodic table
The bigger the energy level, the further the electrons are from the nucleus, and the more energy they have
Also called Principal Quantum Number
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13. Energy Levels in Atoms
The Bohr Model
Ground state - electron occupies lowest possible energy level
Excited state - electron absorbs energy and jumps to a higher energy level
When electron returns to ground state, it releases energy in the form of light.
Emission
Line
Spectra
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14. The Quantum Mechanical Model
Electron does not have an exact orbit.
Atomic Orbital – region of space where there is a high probability of finding an electron.
Electron cloud
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15. Atomic Orbitals
Sublevels
# of sublevels within an energy level is equal to the principle quantum number
For example,
n = 1 has 1 sublevel
n = 2 has 2 sublevels
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16. Sublevels contain orbitals (s,p,d, or f)
Atomic Orbitals
Sublevels
Sublevels contain orbitals (s,p,d, or f)
Each orbital can hold 2 electrons.
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17. There can be several orbital configurations within a sublevel
Atomic Orbitals
Sublevels
There can be several orbital configurations within a sublevel
s – sublevel contains 1 orbital
p – sublevel contains 3 orbitals
d – sublevel contains 5 orbitals
f – sublevel contains 7 orbitals
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18. Atomic Orbitals Summary of Principal Energy Levels and Sublevels
Number of sublevels
Type of sublevel
(n2)
Maximum number of electrons
(2n2)
n = 1 1
1s (1 orbital) 2
n = 2
2s (1 orbital), 2p (3 orbitals) 8
n = 3 3
3s (1 orbital), 3p (3 orbitals),
3d (5 orbitals) 18
n = 4 4
4s (1 orbital), 4p (3 orbitals),
4d (5 orbitals), 4f (7 orbitals) 32
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19. Quantum Numbers

20. Early Models of the Atom
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