atoms - matter is made up of elements and elements in turn are made up of atoms. - macroscopic world...
TRANSCRIPT
ATOMS
- Matter is made up of elements and elements in
turn are made up of atoms.
- Macroscopic world v. Microscopic world
- The unraveling of the structure of the atom is like
working on a jigsaw puzzle, only this puzzle took
almost 50 years to complete and not just by one
scientist alone.
ATOM
Take a piece of chalk. from a Greek word “atomos” which
means indivisible The smallest unit of an element that
still has the properties of that element 1-inch line of gold = 88 million atoms
MOLECULE
Is a unit of a substance that can exist freely and posses all the properties of a given substance
a neutral chemically bonded group of atoms that acts as a unit
There are molecules that consist of only one atom, not group of them.
MOLECULES
Examples1. He = O O O O = 4units/molecules
each has 1 atom2. O2 = = 2 molecules each
contains 2 atoms 3. P = = 2 molecules each
has 4 atoms
What is the true picture of an atom?
Today, the field ion microscope (by
Erwin Mueller, 1956) and the Scanning
Tunneling microscope (STM) (by the
IBM scientists, 1980’s), give us clear
images of the atom
DEVELOPMENT OF THE ATOMIC STRUCTURE
I. Early Ideas about the Atom
- (460 – 370 B.C.) Democritus of Abdera, Greece, a
famous teacher of “Atomists school of thought
suggested the idea of the atoms using a piece of gold
- Claimed that atoms are invisible, indestructible
fundamental or smallest particles of matter
- His theory was ignored because he lacked
experimental proof to back it up.
DEVELOPMENT OF THE ATOMIC STRUCTURE
Plato and Aristotle - Both were prominent philosophers,
demanded that atoms be shown to them.
- Rejected the atomism claiming that this idea challenged the existence of God.
- Said that you can divide anything endlessly.
DEVELOPMENT OF THE ATOMIC STRUCTURE
Later, atomic idea was picked up by
other scientists like Galileo, Francis
Bacon, Robert Boyle, and Isaac Newton
who used the atomic idea to understand
and explain visible events.
DEMOCRITUS’ ATOMIC MODEL
DEVELOPMENT OF THE ATOMIC STRUCTURE
II. DALTON’S ATOMIC THEORY
- (1766-1844) John Dalton, an English school teacher
at age 12 revived the idea of the atom after 2200
years.
- Major Assumptions of DAT (1805)
1. Matter consists of tiny, indestructible particles called
atoms. They remain unchanged during chemical
reactions.
DEVELOPMENT OF THE ATOMIC STRUCTURE
2. Atoms of a particular element all have the same properties (size, shape, mass) different from those of other elements.
3. Atoms combine in simple/small number ratios when they form compounds.
4. A chem’l change involves the joining, separation or rearrangement of atoms in the compounds.
DEVELOPMENT OF THE ATOMIC STRUCTURE
Despite its flaws, this theory was accepted for it explained adequately 2 important laws of chemical combination.
1. The Law of Conservation of Mass2. The Law of Constant/Definite
Composition
DEVELOPMENT OF THE ATOMIC STRUCTURE
The Law of Conservation of Mass- States that no new atoms are gained or
lost during a chem’l rxn, thus the mass during the rxn is unchanged. Atoms merely regrouped themselves.
- Wood + O2 = ashes + smoke+ vapor (total mass) = (total mass)
DEVELOPMENT OF THE ATOMIC STRUCTURE
The Law of Constant/Definite Composition (Joseph Proust, 1794)
- States that a pure compound always consists of the same elements combined in the same mass ratio.
- Ex. H2O = 2H + 1O (2:1) NaCl = 1Na + 1Cl (1:1)
DALTON’S ATOMIC MODEL
Dalton strengthened
Democritus’ idea
REVISIONS OF THE D.A.T.
1. Atoms are divisible, consist of subatomic particles.
2. Atoms of the same elements have different masses. Isotopes
3. Atoms are not permanent. They can be converted to another atoms or be destroyed after certain nuclear processes. Ex. Ra - Rn - Po
ISOTOPES
are atoms of the same element but with different masses.
have the same number of protons/atomic no. but different number of neutrons/mass no.
Ex. H – protium, 0 neutron H - deuterium, 1 neutron H - tritium, 2 neutrons
YOUR TURN
10 – ITEM QUIZ
QUIZ
DIRECTIONS: Answer the ff. correctly.1. Draw Democritus’ atomic model.2. Draw Dalton’s atomic model.3. Name the 2 philosophers who rejected
Democritus’ atomic idea.4. Who is the father of atomic theory?5. Who is the father of the modern atomic
theory?
QUIZ
6. This law states that mass is conserved during a chemical rxn.
7. Atom comes from a Greek word ___
8. Give an example of a one-atom molecule.
9. Give one microscope used to see atoms.
10. 1-inch line of gold has how many atoms?
Tomorrow
Let’s talk about Thomson,
Rutherford, and Bohr