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P. Sci.

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Title: P. Sci.


1
P. Sci.
  • Unit 8
  • Chapter 4
  • Atoms

2
Atomic Structure timeline
  • Ancient Greece - Democritus proposed the atom a
    tiny solid particle that could not be subdivided.
  • 1904 J.J. Thomson discovered that atoms
    contained small, negatively charged particles
    called electrons.

3
  • 1911 Ernest Rutherford proposed that the atom
    had two parts the nucleus in the center (most
    of the mass) surrounded by the electrons.
  • 1913 Niels Bohr
  • hypothesized that
  • electrons traveled in fixed
  • orbits around the atoms nucleus.

4
  • 1913 James Chadwick concluded that the
    nucleus contained positive protons and neutral
    neutrons.
  • 1926 Erwin Schrodinger developed the quantum
    mechanical model which is based on the wavelike
    properties of the electron. (not a particle
    leads to quantum physics)

5
  • 1927 Werner Heisenberg (the Heisenberg
    uncertainty Principle) described that it is
    impossible to know precisely both an electrons
    position and path at a given time. Led to the
    electron cloud theory.

6
Atoms
  • The smallest particle that has the properties of
    an element.

7
Daltons Atomic Theory
  • Every element is made of tiny, unique, particles
    called atoms that cannot be subdivided.
  • Atoms of the same element are exactly alike.
  • Atoms of different elements can join to form
    molecules

8
Parts of an Atom
  • Nucleus small, dense center of an atom made up
    of 2 subatomic particles that are almost
    identical in size and mass.
  • Protons have a
  • positive charge
  • Neutrons have no charge

9
Parts of an Atom cont.
  • Electrons are tiny particles that have very
    little mass that moves around the outside of the
    nucleus. These particles are negatively charged
    and form a
  • cloud around
  • the nucleus.

10
  • The number of protons and electrons an atom has
    is unique for each element.

11
Atomic Charge
  • Atoms have no overall charge because the protons
    () cancel out the electrons (-).

Helium 2 protons - 2
2 neutrons - 0 2 electrons
- -2 total charge 0
12
Protons
  • positive () charge
  • Found in the nucleus
  • of protons atomic
  • The number of protons identify the element
    (atomic )

13
Neutrons
  • no charge
  • Found in the nucleus
  • Along with protons makes up atomic mass
  • protons and neutrons are made up of quarks
    which three quarks determines whether it
    becomes a proton or a neutron.

14
Electrons
  • negative () charge
  • travel in orbitals (or energy levels) around the
    nucleus. (electron cloud)
  • valence electrons - the of electrons in the
    outer shell oxidation

15
  • Unit of measure for atomic particles is Atomic
    mass unit (amu) protons and neutrons about 1
    amu (electrons are about the size of 1 quark)

16
Chemical symbols
  • The one or two letter abbreviation of the element
    name.

17
Mass Number or Atomic Mass
  • the sum of the number of protons and the number
    of neutrons in the nucleus of an atom.
  • of neutrons
  • mass - atomic

Neutrons
Protons
18
Average atomic mass
  • the weighted - average mass of the mixture of all
    an atoms isotopes. The average atomic mass is
    close to the mass of its most abundant isotope.

19
Isotopes
  • Atoms of the same element that have a different
    of neutrons. (identified by the element name
    followed by the mass )
  • ex. C-12, C-14, B-10, B-11)

Carbon 14 8 neutrons
Carbon 12 6 neutrons
20
The End
For now
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