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Transcript
The Atom
Structure of an atom and the
Atomic timeline
Review
Two or more
elements
Element
Compound
What is an element made up of?
Today we will learn…
• That an element is made up of atoms
• Parts of an atom
• How the atom was discovered – atomic
timeline
What is an atom?
• An atom is the smallest particle into which
an element can be divided and still be the
same substance.
rkm.com.au
Atoms are building blocks of matter
because…
MATTER
• Atoms make up
elements
• Elements make up
compounds
• Elements and
compounds make up
matter.
Compound
element 1
element 2
Atom 1
Atom 2
Parts of an atom
• Nucleus is the small, dense, positively charged
center of the atom.
• Protons are positively charged particles in the
nucleus.
• Neutrons are particles in the nucleus of an atom
that have no charge.
• Electrons are negatively charged particles found
in electron clouds outside the nucleus.
http://www.chem4kids.com/files/atom_structure.html
Let’s compare the parts of the atom
Charge
Proton
Positive
Mass
Location
1 amu
Nucleus
Neutron No charge/ 1 amu
Neutral
Nucleus
Electron Negative
Electron clouds
(external to
nucleus)
Almost
zero
1 atomic mass unit (amu) = 1.7 X 10-24 g
Properties of an atom
• Most of the atomic mass is present in the
nucleus because the mass of the electron
is almost equal to zero.
• Mass of a proton = mass of a neutron=
1a.m.u
• The atom has no charge (neutral) because
number of protons = number of electrons.
http://www.chem4kids.com/files/atom_structure.html
There is something even smaller
than protons and neutrons…
• Quarks are smaller particles that make up
protons and neutrons.
Quick review
•
Which of these is NOT one of the basic
pieces of an atom?
1.
2.
3.
4.
Electron
Proton
Quantron
Neutron
Quick review
•
If I ask you to draw a nitrogen atom, what
would you show in the nucleus of the
atom?
1.
2.
3.
4.
Molecules
Neutrons
Protons
Electrons
Story of the atom
• Also known as the Atomic Timeline
1911
440
BC
1803
1897
1913
20th century
Democritus
440 BC
• Proposed the “atom”
• Atoms
– are small, hard particles
– constantly move
– are “uncuttable”
1911
440
BC
1803
1897
1913
20th century
John Dalton
1803
• Conducted experiments in
combining elements
• All substances are made up
of atoms
• Atoms of the same element are exactly alike
• Atoms of different elements are different
• Elements combine in specific proportions
1911
440
BC
1803
1897
1913
20th century
J. J. Thomson
1897
• Conducted the cathode ray tube
experiment
• There are small, negatively
charged particles inside the atom
• “Plum pudding” model
1911
440
BC
1803
1897
1913
20th century
E. Rutherford
1911
• Gold foil experiment
• Atoms contain mostly empty
space
• Small, dense positively charged nucleus
• Most of the atom’s mass is in the nucleus
• Electrons move around in empty space in
the atom
1911
440
BC
1803
1897
1913
20th century
N. Bohr
1913
• Electrons travel in definite paths
• Electrons jump between levels
from path to path
1911
440
BC
1803
1897
1913
20th century
Schrödinger and Heisenberg
20th century
• Electron paths
cannot be
predicted
• Electrons are found
in electron
clouds, not paths
1911
440
BC
1803
1897
1913
20th century
Quick Review
•
How is the modern model of an atom
different from the Bohr atomic model?
1. The masses of the atomic particles are
different.
2. The numbers of electrons are different.
3. The shapes of the nuclei are different.
4. The arrangements of the electrons are
different.
Atomic Timeline
worksheet
• Complete this in class. If it is not done in
class then it will become a homework?
Wrapping up
• What we learned today
– What is an atom?
– Parts of an atom
– Atomic timeline
• Homework
I’m
positive!
I’m
negative!
I could
care less!
– Timeline?
• Next time
– Continue with more information about the atom
– Learn about how atoms help elements find their spot
on the Periodic Table