Unit 3: History of the Atomic Model

A
X
B
A: Atomic Mass
B: Atomic Number
X: Element

What is the average atomic mass?
the weighted average of each isotope of the element in proportion to the percentage of each isotope of the element occuring in nature

How do you find the average atomic mass of an element?
1. Find the % abundance and atomic mass for each isotope
2. Multiply the abundance by the atomic mass
3. Find the sum of the products
4. Divide the sum by 100

Describe Rutherford’s findings
-concluded an atom must have a nucleus and the atom’s mass was concentrated at the center
=suggested electrons orbited around the nucleus

What is the emission spectrum?
The specific wavelengths of light that elements emit

What is the Absorption spectrum?
The specific wavelengths of light that elements absorb

What correlation did Neil Bohr suggest between the electrons in atoms and their light behavior
-When electron move from higher level to lower, energy is emitted
-When electrons move from a lower level to a higher level, energy is absorbed

What is the Quantum of Energy?
specific amount of energy emitted or absorbed by electrons moving between energy levels

What is GRIT?
Passion and perseverance for very long term goals. Having stamina, sticking with your future, day in and day out, not for a week, not for a month, but for years

What is ionization energy?
the amount of energy it takes to remove one electron from a neutral atom

What is electronegativity?
how strong a atom holds onto their electrons

Describe Thale’s contributions to the development of the Atomic Theory
believed everything came from water

Describe Democritus’s contributions to the development of the Atomic Theory
-Corpuscles Atoms: matter consisted of invisible and indivisible small particles
-based solely on imagination
-believed there was empty space in atoms
-atoms were in constant motion

Describe Aristotle’s contributions to the development of the Atomic Theory
-disagreed with Democritus
-four main elements: earth, water, fire, and air

Describe Epicurus’s contributions to the development of the Atomic Theory
-proposed atoms had mass, moved at a consistent speed, and were able to change direction

Describe John Dalton’s contributions to the development of the Atomic Theory
-proposal of the modern atomic theory
1. All mater is composed of particles called atoms
2. Atoms of a given element have unique properties (differ in size, mass, etc)
3. Atoms of different elements combine in simple, whole-number ratios to form chemical compounds
4. Atoms cannot be subdivided, created, or destroyed
5. During chemical reactions, atoms are combined, separated, or rearranged
-based his theory on observations from his experiments with gasses and meteorology
-His theory supposes the Law of Conservation of Mass

Describe JJ Thomson’s contributions to the development of the Atomic Theory
-discovered first subatomic particle (electron) with the usage of a cathode ray tube(tube with beam of electrons). With a battery attached, electrons would run through the wire. Thomson then used oppositely charged metal particles and magnets and saw that he could deflect the beam.
-Plum Pudding Model: negatively charged particles were dispersed throughout an atom embedded within matter that was positively charged

Describe Robert Millikan’s contributions to the development of the Atomic Theory
-oil drop experiment revealed the mass and charge of electrons

Describe Ernest Rutherford’s contributions to the development of the Atomic Theory
-student of JJ Thompson
-“Father of Modern Physics”
-Gold Foil experiment: results showed that atoms contain a dense central region where most of the mass was located and was positively charged
-Directed a narrow beam of positively charged particles through a thin piece of gold foil.
-Proposed nuclear model: atoms had a positively charged nucleus surrounded by electrons (did not discuss the electron structure)

Describe James Chadwick’s contributions to the development of the Atomic Theory
discovery of neutrons in the nucleus

Describe Neil Bohr’s contributions to the development of the Atomic Theory
-studied the relationship between light emission of an element and the absorption and release of energy
-Planetary (Orbital Model): electrons orbited the atom’s nucleus in circle patterns
-could only be applied to the hydrogen atom

Describe Albert Einstein’s contributions to the development of the Atomic Theory
-used Bohr’s ideas to explain the photoelectric effect
-Photoelectric Effect: some metals are exposed to certain light frequencies which cause electrons to be emitted
-theorized electrons escaped from their atom

Describe Louis de Broglie’s contributions to the development of the Atomic Theory
-Quantum Theory: electrons exist as both particles and waves and describes the energy levels for all the elements and the probable locations of the electrons
-based on Heisenberg Uncertainty Principle: the exact location and speed an electron are impossible to determine at the same time