Download Atoms, Molecules, Compounds, Elements, and Mixtures

Atoms
Elements
Molecules
Compounds
ATOM
An atom is the smallest particle
into which an element can be
divided and still be the same
substance.
Atoms
• Atoms are basic
building blocks
of matter that
make up
everyday
objects.
Atoms
• Atoms have
three parts.
• They are
Protons,
Neutrons, and
Electrons.
Electrons
• Electrons orbit around an
atom. In this picture, they
are the small yellow bits.
• They have a negative charge.
• They are lighter than protons
or neutrons.
• The number of
protons=number of electrons
in a neutral atom
Electron Energy Levels
Valance Electrons
• Are the electrons in the last shell or energy
level of an atom.
• They do show a repeating or periodic
pattern.
• The valence electrons increase in number
as you go across a period.
• Elements in the same column on the
periodic table have the same number of
valance electrons.
Protons
• They are positively
charged.
• Are located in the nucleus.
• Atomic Number=Number
of protons
• In this picture, the protons
are the blue pieces in the
center of the atom.
Neutrons
• Neutrons are neither
positive nor negative.
• Neutrons are in the
nucleus of an atom.
• The atomic mass –
number of protons =
number of neutrons
• In this picture, neutrons
are the purple pieces in
the center of the atom.
Subatomic Particles (Table 2.1)
Particle
Mass
(g)
Charge
(Coulombs)
Charge
(units)
Electron (e-) 9.1 x 10-28 -1.6 x 10-19
-1
1.67 x 10-24 +1.6 x 10-19
+1
Proton (p)
Neutron (n) 1.67 x 10-24
0
0
mass p = mass n = 1840 x mass e-
2.2
Ions
Loss or gain of
an electron
makes an atom
into an ion.
Gaining an
electron
makes a
positive or
negative ion?
+
-
Losing an
electron
makes a
positive or
negative
ion?
Isotopes
Atoms that gain or
lose a neutron
become isotopes.
Radioactive
isotopes are used in
medicine for
imaging (such as
PET scanners).
https://www.youtube.com/watch?v=cnXV7Ph3WPk
https://www.youtube.com/watch?v=d3YR8e_iHlk
https://www.youtube.com/watch?v=D-iPPwDAk1Q
https://www.youtube.com/watch?v=Le9a8C0Pk2c
History of the
Atomic Theory
Dalton
John Dalton
developed his
atomic theory
from observations
gathered from
many
experiments.
http://www.britannica.com/eb/art/print?id=15469&articleTypeId=0
Dalton’s ATOMIC THEORY
1. All substances are made of atoms.
Atoms are small particles that
cannot be created, divided, or
destroyed.
Dalton’s ATOMIC THEORY
2. Atoms of the same element are
exactly alike, and atoms of
different elements are different.
Dalton’s ATOMIC THEORY
3. Atoms
join with other atoms to
make new substances.
J.J. Thomson
o In 1897, J.J. Thomson made a
discovery that identified an error in
Dalton’s theory.
o There are small
particles inside
the atom.
Thomson’s Results
o Thomson discovered atoms can be
divided into even smaller parts.
o What he discovered was the “electron.”
Thomson called it a “corpuscle” back then.
Revision of the Atomic Theory
Because Thomson knew atoms have no
overall charge, he realized that
positive charges must be present to
balance the negative charges of the
electron.
Rutherford (1909)
Ernest Rutherford,
a former student of
Thomson, designed an
experiment to investigate
the structure of the atom.
http://www.pbs.org/wgbh/aso/databank/entries/bpruth.html
Revision of the Atomic Model
Rutherford proposed the center of
the atom is a tiny, extremely
dense, positively charged region
called the “NUCLEUS.”
Rutherford’s Model
Bohr (1913)
Neils Bohr was a Danish
scientist who worked
with Rutherford.
He suggested electrons
travel around the
nucleus in definite
paths.
http://www.pbs.org/wgbh/aso/databank/entries/bpbohr.html
These paths are located in levels
at certain distances away from
the nucleus.
Bohr’s Atomic Model
electron
neutron
proton
Chadwick (1932)
James Chadwick, an English
scientist, discovered the
“NEUTRON.”
He won the Nobel Prize for Physics in 1935, and
his research prepared the way for the
development of the atomic bomb.
http://nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick-bio.html
Still more changes…
Many 20th century scientists have contributed to
our current understanding of the atom.
http://particleadventure.org/frameless/modern_atom.html
Electrons do not travel in definite
paths around the nucleus like Bohr
thought
This discovery was made by
scientists Erwin Schrodinger and
Werner Heisenberg.
In the modern atomic theory…
The exact path of a moving electron cannot be
predicted, but there are regions inside the
atom where electrons are likely to be found.
These regions are called electron clouds.
https://www.youtube.com/watch?v=07yDiELe83Y
Elements
What is a Pure Substance?
• A pure substance is a classification of
matter that includes both elements and
compounds
• Pure substances cannot be separated by
physical means such as distillation,
filtration, or chromatography
Elements
• An element is a
substance
made up of
only one kind of
atom.
• Elements make
up all
substances on
the earth.
Elements
• Located on the periodic table
• Each has its own Atomic Number.
• Divided into Metal, Non-Metal, and
Metalloid
https://www.youtube.com/watch?v=d0zION8xjbM
https://www.youtube.com/watch?v=zGM-wSKFBpo
https://www.youtube.com/watch?v=zUDDiWtFtEM
Molecules
Molecules
• Are made up of atoms bonded
together.
• The structure of an individual atom
determines:
–Whether the atom can form
bonds.
–How many other atoms it can
bond to.
Molecules
• A molecule is the
smallest particle of
a substance that
exists alone.
• This is a picture of a
water molecule. It
is two parts
hydrogen and one
part oxygen.
Molecules
NaCl, salt
Molecule: The smallest
identifiable unit that retains
the physical and chemical
properties of
the pure
substances.
Ethanol, C2H6O
Buckyball, C60
Diatomic Molecules
Are molecules of two
atoms of the same
element. Elements found
is nature as diatomic are,
H2, O2, N2, F2, Cl2,Br2and I2.
https://www.youtube.com/watch?v=H57ZUlBQXGM
Compounds
Compounds
• A compound is two
or more elements
combined together.
• This is a picture of a
salt compound.
Compounds
• Is a combination of 2 or more
elements in definite ratios by mass.
• The character of each element is lost
when forming a compound (e.g.,
think of NaCl).
Compounds
• A compound is a substance
whose smallest unit is made
up of atoms of more than
one element bonded
together.
• Compounds often have
properties that are different
from the elements that
make them up.
• Examples: Water, salt, sugar
Compounds Have Formulas
• H20 is the chemical
formula for water, and
H2O2 is the formula for
hydrogen peroxide.
• The formula tells you
which elements make
up a compound as well
as how many atoms of
each element are
present.
How to read a formula
H 20
This is a subscript. It tells us
how many atoms of that
element exist in one unit of
that compound.
Hydrogen is made of 2 H
atoms and 1 O atom.
No subscript is used when only
one atom of an element is
present.
Let’s try it…
• Using your white board tell how many atoms there
are in each element.
• Sulfuric Acid H2SO4
– 2 Hydrogen
– 4 Oxygen
• Hydrogen Peroxide H2O2
– 2 Hydrogen
– 2 Oxygen