Atoms

1
Atoms
2
Atom Model

• Name the three particles that make up the atom.
• Where are these particles located in the atom?
• What charges do the particles have?

3
Atoms Their Components

• Atoms are the blocks out of which pretty much
  everything is made.
• Atoms are incredibly small.They cant be seen
  with the naked eye alone.
• Because of atoms there are things like stars,
  ocean, mountains, plants, animals, people, and
  classrooms.

4
Bohr Model

• Pictures help us understand how atoms work.
• When looking inside an atom at its parts, it is
  easier to use a system of dots and rings, called
  the Bohr model, named after Niels Bohr.

5
Components of an Atom

• There are three parts of an Atom
• Protons Positive Charge
• Neutrons Neutral Charge
• Electrons Negative Charge

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Proton, Neutron, Electrons

• The center of the atom is named the nucleus.
  Protons and neutrons live in a ball at the
  nucleus.
• The electrons live in shells at different
  distances from the nucleus.
• In the Bohr model, we group electrons in rings
  around the nucleus. Each shell can only house so
  many electrons.
• An atom tries to have as many electrons as
  protons.

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Electron Shells

• The outermost shell of an atom is special.
• This is where the electrons involved in molecular
  bonding live. These electrons are free to create
  bonds that make molecules.
• The shell is called the valence shell. When the
  valence shell is full, the atom makes no
  molecules.
• The empty spots in the valence shell (the outer
  shell) invite other atoms electrons to fill it.
  When electrons do that, a molecule is born.

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Atomic Number

• The atomic number is the number of protons in an
  atom.
• The atomic mass number (units) is the number of
  protons and neutrons together in an atom.
• The larger the nucleus, the more protons it has.
  Each time you add a proton to an atom, you end up
  with a totally new element.

9
Review

• Neutrons and protons live in the nucleus.
• The nucleus is the center core of the atom.
• Electrons orbit the nucleus in layers called
  shells.
• Electrons fill the inner shells first.
• Electrons equal protons in number in a stable
  atom.
• Protons and neutrons may equal or be nearly equal
  in number.

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Periodic Table
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Isotope

• An isotope is an atom that contains an unusual
  number of neutrons for that element.
• Making isotopes, adding neutrons, does not give
  us a completely new atom. Addition of protons is
  what gives us new atoms.

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How to read a Periodic Table

• Column tells how many electrons live in the
  valence shell (also called Group)
• Row tells how many shells surround the atom
  (also called Period)
• Atomic Number Moving right by one increases
  proton number. The number of protons equals the
  number of electrons in a stable atom.
• Atomic Mass Number The weight of an atom,
  counting its protons and neutrons.
• Noble Elements Having filled valence shells,
  these form NO bonds with other atoms.

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Rows of The Periodic Table

• Look at the first row of the PT. The top row
  contains only two elements, placed far apart,
  hydrogen (H) and Helium (He). Both these
  elements have only one electron shell each.
• The row starting with Lithium (Li) and ending
  with Neon (Ne) contains elements with two shells.
  
• Each row down the chart means another shell for
  its electrons.
• In the bottom row, the elements have seven
  electron shells each.

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Ionic Bond

• Columns account for the number of electrons in
  the outer valence shells.
• In the column under hydrogen, these elements have
  only one electron in their valence shells. These
  atoms lose their single electron easily in an
  ionic bond. An ionic bond forms between two
  atoms that are oppositely charged.
• Scientists call elements at this end of the chart
  alkali or bases.

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• In the middle of the chart are metals.
• The alkaline earth metals under Beryllium (Be)
  have earthy and metallic properties.
• Nonmetals slant across the chart, starting with
  Boron (B) going through Silicon (Si), Tellurium
  (Te), Astatine (As), and Actinium (At).
• The elements under Flourine (F) pick up electrons
  to form negative ions. An ion is an atom or
  group of atoms that has acquired an electric
  charge by gaining or losing one or more
  electrons.
• The so called halogens under Flourine form salts
  with alkali metals.
• The last column under Helium (He) contains
  elements with eight electrons in the outer shell.
  These are called the Noble Gases. The number of
  outer electrons here means that these do not form
  bonds with other atoms.

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Questions

• 1. What is a protons charge?
• 2. Where are protons located?
• 3. Do electrons have a charge? If so, what?
• 4. Where are electrons located in atoms?
• 5. Does the number of electrons matter?
• 6. Where is the most of the mass of an atom?

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• 7. What is the charge of a neutron?
• 8. What is an atom?
• 9. What is an ion of an atom?
• 10. What is an isotope of an atom?
• 11. For a given element, can you have a
  different number of protons for that element? Why?