Six Weeks Review PPT
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Transcript Six Weeks Review PPT
STRUCTURE OF AN ATOM
A brief review of the structure of atoms
HISTORY OF ATOMIC THEORY
See the Powerpoint on Atomic Theory Scientists for more
information and pictures/models.
Review/Summary:
Democritus, 460 BC – proposes particles so small they can not
be destroyed or divided, and describes them as “atomos”
(uncuttable)
John Dalton, early 1800’s - first to use “atom”; proposes that
atoms of the same element are identical, and atoms of
different elements have different weights/masses; Solid
Sphere Model
JJ Thomson, ~1897 – discovers the first subatomic particle,
electrons; Plum Pudding Model
Ernest Rutherford, ~1912 – discovers the proton, and nucleus;
Nuclear Model
Niels Bohr, ~1915 – discovers energy levels for the electrons;
Planetary Model
Erwin Schrodinger, ~1926 – developed the Electron Cloud
Model
James Chadwick, ~1932 – discovers the neutron in the
nucleus
Most Modern Model – The electron cloud model with
all three subatomic particles
DEVELOPMENT OF ATOMIC THEORY
A more extensive review of Atomic Theory
Development:
http://www.abcte.org/files/previews/chemistry/s1_p1.
html
Use the “next” button at the bottom of the webpage
above to cycle through the different scientists and their
theories/models.
WHAT IS AN ATOM?
Smallest particle of an element (pure
substance) that still has the properties of that
element.
Most of the atom is made of EMPTY
SPACE
Example: an atom of gold is the smallest particle
of gold (an element or pure substance) that still
has the properties of gold.
Video: http://www.youtube.com/watch?v=o3I1JGW-Ck
Brainpop (username: sclee
password: cougars):
Atom:
http://www.brainpop.com/science/matterandchemistry/at
oms/
Atomic Model:
http://www.brainpop.com/science/matterandchemistry/at
omicmodel/
TWO MAIN REGIONS OF THE ATOM
Nucleus
Positive charge
Almost all of the mass of an atom
Tiny, dense center of the atom
Can be broken apart in chain reactions to produce
HUGE amounts of energy for use in electricity,
medicine, weapons, etc (nuclear energy)
Electron cloud
Negative charge
Almost 0 mass
Energy levels/shells
Max # electrons – 2,8,8*
Valence level – outermost energy level
THE NUCLEUS OF AN ATOM
Tiny and dense
Center of the atom
Contains protons and neutrons
Positive charge (positive protons plus neutral neutrons)
Very little of the volume (space) in an atom, but almost all of the
mass
Mass = protons + neutrons
Units for mass are amu (atomic mass unit)
Held together by a strong nuclear force
Can be split apart in controlled chain reactions to release nuclear
energy:
http://www.youtube.com/watch?v=ufEAg9h9wU8
http://www.youtube.com/watch?v=mBdVK4cqiFs
Fermi is the first scientist to conduct controlled chain
reactions
Nuclear energy in weapons:
http://www.brainpop.com/science/energy/radioactivity/
Video tutorial: http://www.youtube.com/watch?v=FSyAehMdpyI
ELECTRON CLOUD
Most of the volume in the atom, but almost 0
mass
Contains only electrons
Negative charge
Energy levels
Closest to the nucleus is the lowest level
Outermost level is the valence level
SUBATOMIC PARTICLES
Protons
Neutrons
Electrons
Video tutorial:
http://www.youtube.com/watch?v=FSyAehMdpyI
ISOTOPES
Atoms of the same element can have different
numbers of neutrons.
Naming isotopes: use the name of the element,
followed by the mass number of that atom
This means their mass is also different (mass =
protons + neutrons)
Ex: Carbon-12, Carbon-13
Video Brainpop:
Isotopes:
http://www.brainpop.com/science/matterandchemistr
y/isotopes/
Radioactivity:
http://www.brainpop.com/science/matterandchemistr
y/periodictableofelements/
IONS
In a neutral atom, the number of protons equals the
number of electrons.
Neutral atoms are often unstable, because they do not have
a full valence level.
Unstable atoms will gain or lose electrons to become
stable.
Atoms which have gained electrons (gained negative
particles) are negative ions. They will have more
electrons than protons.
Atoms which have lost electrons (lost negative
particles) are positive ions. They will have fewer
electrons than protons.
To see if it is an ion, compare protons and electrons.
Video Tutorial Brainpop:
Ions:
http://www.brainpop.com/science/matterandchemistry/ions/
PERIODIC TABLE ARRANGEMENT
Dimitri Mendeleev developed the first (near)
modern Periodic Table of Elements
Page 71 in your book
Based on physical properties, especially atomic mass
(later rearranged by atomic number)
Periods are rows, and tell how many energy
levels the neutral atom has; elements increase
left to right across the periods and are very
different in properties/reactivity;
Groups or families are columns; atoms in the
same group have the same number of valence
electrons, and similar chemical reactivity.
CHEMICAL REACTIVITY ON THE PERIODIC TABLE
Metals on the left (2/3 of the table), metalloids on the break,
metals on the right (except hydrogen).
Most reactive metals – group 1, with 1 valence electron;
Most reactive nonmetals – group 17, with 7 valence electrons;
Nonreactive (inert) elements – group 18, with full valence level
METALS, NONMETALS, METALLOIDS ON THE
PERIODIC TABLE
Property
Metals
Metalloids
Nonmetals
Luster (shine)
Yes
No
No
Malleable
Yes
No (brittle)
No (brittle)
Ductile (wires)
Yes
No
No
Conductivity
Yes
Semi-
No
State at rom
temp.
Solid (except
mercury)
Solid
Solid, liquid, or
gas
PERIODIC TABLE TRENDS
Atomic Mass Increases
Atomic number increases
Atomic number increases
Atomic Mass Increases
Metallic Properties Increase