Transcript Chapter 4: Atomic Structure

Electron
Proton
Defining the atom:
-An atom is the
smallest particle of
an element that
retains its identity
in a chemical
reaction.
Dalton s atomic theory was the first
theory to relate to chemical changes
to events at the atomic level.
Democritus believed that
atoms were indivisible and
indestructible.
Once upon a time there
was an English chemist by the
name of John Dalton who was
primarily known for his atomic
theory.
1.) All matter is made of atoms. Atoms are indivisible and
indestructible.
2.) All atoms of a given element are identical in mass and
properties.
3.) Compounds are formed by a combination of 2 or more
different kinds of atoms.
4.) A chemical reaction is a rearrangement of atoms.
1.) How did Democritus characterize atoms?
2.) In your own words state the main ideas of Dalton’s
Atomic Theory.
3.) According to Dalton’s theory, is it possible to
convert atoms of one element into atoms of another?
Explain.
4.) What Charge does a neutron have? Proton? And
electron?
5.) What is an atom?
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Structure Of An Atom
Three types of subatomic particles:
Thomson 1897: performed
experiments that involved
passing electric current through
gases at low pressure. The
result was a cathode ray or
glowing beam. Thomson
concluded that a cathode ray is
a stream of tiny negatively
charged particles moving at high
speed. He later named them
electrons and concluded that
electrons must be parts of the
atoms of all elements.
-Electrons
-Protons
- Neutrons
Thomson's plum
pudding model
demonstrated
corpuscles
scattered randomly
throughout the
atom like plums
scattered
throughout the
pudding.
Rutherford's gold foil experiment
yielded evidence of the atomic
nucleus. Rutherford and his coworkers
aimed a beam of alpha particles at the
sheet of gold foil surrounded by a
fluorescent screen. Most of the
particles passed through the foil with
no deflection at all. A few particles
were greatly deflected. Rutherford
concluded that most of the alpha
particles pass through the gold foil
because the atom is mostly empty
space. The mass and positive charge
are concentrated in a small region of
the atom. Rutherford called this the
nucleus. Particles that closely
approach the nucleus are deflected.
Rutherford proposed later that the
atom is mostly empty space. He called
the region the nucleus. (a tiny central
core of an atom and is composed of
protons and neutrons) Rutherford’s
atomic model is known as the nuclear
atom. In the nuclear atom, the protons
and neutrons are located in the nucleus.
The electrons are distributed around
the nucleus and occupy almost all of the
volume of the atom.
1.) What are three types of subatomic particles?
2.)How does the Rutherford model describe the
structure of atoms?
3.) What are the charges and masses of the three
subatomic particles?
4.) Describe the plum pudding model.
5.) How did Rutherford's model of the atom differ from
Thomson’s?
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Distinguishing Among Atoms
tomic Number- of an
element is the number of
protons in the nucleus of an
atom of that element. The
atomic number identifies an
element.
ass number- the total
number of protons and
neutrons in an atom.
Elements are different
because they contain different
number of protons.
Au is the chemical
symbol for gold.
How many electrons
does a gold atom
have
197
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Atomic mass- the weighted
average of the masses of the
isotopes of an element.
Are atoms that have the
same number of protons
but different numbers
of neutrons.
calculate the atomic
mass of an element,
multiply the mass of
each isotope by its
natural abundance,
expressed as a
decimal, and then
add the products.
Because isotopes
of an element
have different
numbers of
neutrons, they
also have
different mass
numbers.
A periodic table is an arrangement
of elements in which the elements
are separated into groups based on
a set of repeating properties.
Period: each horizontal
row of the periodic table
Group: Each vertical
column of the periodic
table
-A periodic table allows you to easily
compare the properties of one element (
or group of elements) to another
element (or group of elements)
1.) What distinguishes the atoms of one element
from the atoms of another?
2.)What equation tells you how to calculate the number of
neutrons in an atom?
3.)How do the isotopes of a given element differ from one
another?
4.) How is atomic mass calculated?
5.)What makes the periodic table such a useful tool?
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