CHAPTER 5 & 6
ELECTRONS IN ATOMS &
THE PERIODIC TABLE
5.1 Models of the atom
The Development of Atomic Models
BIG PROBLEM:
**Rutherford’s atomic model could not explain the chemical
properties of elements.**
BIG QUESTION:
Why do elements produce different colors when heated?
(a.k.a why do metals turn red when hot)
5.1 Models of the atom
BIG SOLUTION:
In 1913, Neils Bohr (Danish), stated that electrons could occupy fixed
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orbitals without giving off energy.
Conclusions:
- Electrons FARTHER from the nucleus have HIGHER energy, thus…
- Electrons CLOSER to the nucleus have LOWER energy
5.1 Models of the atom
**Like a staircase take energy to climb…electrons need energy to reach higher orbitals**
5.1 Models of the atom
This theory was deduced from flame tests and gas tubes.
Write down your observations of a flame test:
Draw a picture of a gas tube:
5.1 Models of the atom
This theory was deduced from flame tests and gas tubes.
Write down your observations of a flame test:
Draw a picture of a gas tube:
5.3 Physics and the Quantum Mechanical Model
So… Why DO elements produce COLORS when HEATED?
Let’s Brainstorm…take out your phones .
5.3 Physics and the Quantum Mechanical Model
Bohr’s Answer
**Since the amount of energy and electron has determines the
distance it orbits from the nucleus, the electrons: **
1. Take in energy (heat, electricity, or light) and move to higher
energy levels (farther from the nucleus)
2. Release the extra energy as light and fall back to a lower energy
level
5.3 Physics and the Quantum Mechanical Model
We Say:
“Electrons take in energy, jump up, fall back down,
and release energy in the form of light.”
5.3 Physics and the Quantum Mechanical Model
We Say:
“Electrons take in energy, jump up, fall back down,
and release energy in the form of light.”
5.3 Physics and the Quantum Mechanical Model
We Say:
“Electrons take in energy, jump up, fall back down,
and release energy in the form of light.”
5.1 Continued…Models of the Atom
Eventually, we learn the Bohr model is a lie.
Bohr Model
really is
Wave Mechanical Model
(no distinct orbital boundary)
5.1 Continued…Models of the Atom
This model does not show the path of electrons –
Just the most PROBABLE location!
6.1 Organizing the Elements and Classifying the Elements
Origin of the Periodic Table
Dimitri Mendeleev – published the first real periodic table in 1869
- Based upon chemical and physical properties
- Listed elements in order of increasing atomic mass
- Left spaces for undiscovered elements
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6.1 Organizing the Elements and Classifying the Elements
Predicting properties using other elements data:
6.1 Organizing the Elements and Classifying the Elements
Predicting properties using other elements data:
Example: Predict the density of Aluminum given:
Density: Ga = 5.9 g/cm3 & B = 2.3 g/cm3
** Find the Average!!!**
Look…it doesn’t seem like much, but it’s what Mendeleev did.
6.1 Organizing the Elements and Classifying the Elements
Modern Periodic Law:
** Properties are a periodic function of atomic number. **
6.1 Organizing the Elements and Classifying the Elements
Periods:
Groups:
left to right on the periodic table
up and down on the periodic table
elements have the same # of energy levels elements have the same # valence electrons
elements do not have similar properties
elements have similar properties
a.k.a rows, shells, and energy levels
a.k.a families (columns)
6.1 Organizing the Elements and Classifying the Elements
Metals, Metalloids, and Nonmetals
6.1 Organizing the Elements and Classifying the Elements
Families:
5.2 & 6.3 Electron Arrangement in Atoms & Periodic Trends
Valance Electrons:
Electrons that occupy the outmost shell of an atom
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5.2 & 6.3 Electron Arrangement in Atoms & Periodic Trends
Valance Electrons:
Electrons that occupy the outmost shell of an atom
5.2 & 6.3 Electron Arrangement in Atoms & Periodic Trends
Electronegativity:
The ability of an atom to attract electrons.
5.2 & 6.3 Electron Arrangement in Atoms & Periodic Trends
Writing Orbital Notation:
First things First, your PT is missing some things...
5.2 & 6.3 Electron Arrangement in Atoms & Periodic Trends
Writing Orbital Notation:
5.2 & 6.3 Electron Arrangement in Atoms & Periodic Trends
Writing Electron Configuration:
5.2 & 6.3 Electron Arrangement in Atoms & Periodic Trends
Electron Notation in General:
Electrons enter orbitals in a set pattern.
For the most part, they follow the:
- Aufbau Principle
- Pauli Exclusion Principle
- Hund’s Rule
5.2 & 6.3 Electron Arrangement in Atoms & Periodic Trends
Aufbau Principle: electrons must fill lower energy levels before
entering higher levels.
Pauli Exclusion Principle: electrons occupying the same orbital
must have opposite spin.
Hund’s Rule: (better known as the smelly guy on the bus rule)
before any second electron can be placed in a sub level, all the
orbitals of that sublevel must contain at least one electron
5.2 & 6.3 Electron Arrangement in Atoms & Periodic Trends
Practice…