ATOMS Flashcards
A timeline of atomic
models
- Atomic model (1808)
- Plum-pudding model
(1904) - Nuclear model (1911)
- Planetary model (1913)
- Quantum mechanical
model (1926-present)
The total mass of substances does not change during a chemical reaction
Law of Mass Conservation
No matter what its source, a particular chemical compound is composed of the same elements in the same parts)fractions) by mass(proust)
Law of Definite( Constant) Composition
When two elements form a series of compounds, the masses of one elements that combine with a fixed mass of the other element are in the ration of small integers to each other (Dalton)
Law of Multiple Proportions
Democritus 460 - 370 B.C
There are various basic
elements from which all
matter is made
* Everything is composed of
small atoms moving in a void
* Some atoms are round,
pointy, oily, have hooks, etc.
to account for their
properties
* Ideas rejected by leading
philosophers because void =
no existence
1st Concept of an Atom
✔ Atoms are small hard
particles.
✔ Made of a single
material that’s formed into
different shapes and sizes.
✔ They are always moving
✔ They form different materials
by joining together.
“ATOMOS
Aristotle and Plato favored the earth, fire, air and water approach to the nature of matter. Their ideas held sway because of their eminence as philosophers. Atmos was buried approximately 2000 years
The eminent philosophers of the time, Aristotle and Plato has a more respected and ultimately wrong theory
Atomic Model : John Dalton
- Matter is made of small
indivisible atoms. - Atoms can’t be
subdivided, created or
destroyed. - Atoms of the same
element have the same
property.
3.Atoms of different
elements have different
properties. - Atoms of different elements
can form compounds
Plum-pudding model: J.J.
Thomson
- An atom is electrically
neutral. It has no
charge. - In an atom, both
positive charges and
negative charges are
equal. - An atom is made out
of a sphere of positive
charges with
negatively charged
electron embedded in
it
Cathode Ray Tube Experiment
Thomson studied the
passage of an electric
current through a gas.
As the current passed
through the gas, it
gave off rays of
negatively charged
“Goldstein- a ray headed in
the opposite direction
Nuclear model: Ernest
Rutherford
- Atoms are mostly empty
space. - Most of the mass is
concentrated in the
center of atom. This
tiny, dense, positively
charged core called a
nucleus. - Electrons are located
outside the nucleus.
Alpha Particle Experiment
Gold Foil experiment marked the discovery that the atom was made up of mostly empty space and contained a positively charged nucleus
Rutherford Model suggest that atoms are unstable.
Planetary model: Niels Bohr
- Electrons orbit the nucleus in
orbits that have specific size and
energy. - The energy of the orbit is related toits size. The lowest energy is foundin the smallest orbit.
- Electrons reside in orbits. They
move between each shell when
gaining or losing energy. - When gaining energy, electrons
move to farther orbit from the
nucleus. When losing energy,
electrons move to closer orbit fromthe nucleus.
The energy that an electron has is based on it’s location around the nucleus. ( Electrons that are closer to the nucleus have less energy than those that are farther away from the nucleus
Energy Levels
Quantum Mechanical Model:
Erwin Schrödinger
- Electrons don’t move
around the nucleus in
orbits. - Electrons exist in
specific energy levels as
a cloud. - The electron cloud is the
region of negative
charges, which
surrounds the nucleus. - Orbital : The region with
a high probability of
containing electrons
