ATOMS and their tiny parts

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ATOMSand their tiny parts

• by
• Mr. Cox

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Atomos Uncuttable

• A Greek philosopher, Democritus, first
  hypothesized that all matter had small particles.
• He called these small particles atomos since
  they were so small they were uncuttable.

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Inside the Atom
Bohr model

• There is a tiny nucleus in the center (like a
  cell has a nucleus with DNA)
• The nucleus has protons and neutrons0
• Protons have a positive charge (p)
• Neutrons0 have a neutral charge (n0)
• The number of protons identifies each atom

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Around the Atom

• Around the atom are rings or clouds of tiny,
  tiny, electrons-
• Electrons- have a negative charge (e-)
• Electrons- are attracted to protons because
  opposite charges attract!
• The charge of an atom is written as a number in
  the upper right corner.

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Sizes of Subatomic Particles

• Atoms are microscopic! A sheet of paper is
  10,000 thick!
• Protons and neutrons0 in the nucleus are larger
  than electrons- around the nucleus
• Protons and neutrons0 each have a mass
• 1 atomic mass unit (a.m.u.)
• Electrons- have a fraction of that mass! 1 /
  1836th!

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Motion of Subatomic Particles

• Protons and neutrons0 are in the nucleus
  vibrating in place. They vibrate!
• Electrons- race around and can reach the speed of
  light! Speedsters!

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Daltons Theory(from a British school teacher,
John Dalton, in 1802)

• All matter is composed of extremely small
  particles called atoms.
• All atoms of a given element are identical in
  size, mass, and other properties. Atoms of
  different elements differ in size, mass, and
  other properties.
• Atoms cannot be subdivided, created, or
  destroyed.
• Atoms of different elements can combine in
  simple, whole-number ratios to form compounds.
• In chemical reactions, atoms are combined,
  separated, or rearranged.

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Modern Atomic Theory
1. Elements are composed of atoms, which are
extremely small. 2. All atoms of a given
element have the same chemical properties and
contain the same number of protons. 3.
Compounds are formed by the chemical combination
of two or more different kinds of atoms. (Whole
numbers only) 4. Atoms are the units of
chemical change.
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Valence Electrons Bonds

• Electrons- that are farthest from the nucleus are
  named valence electrons- and they are involved
  in bonding.
• Valence electrons- can be given or taken in a
  chemical bond called an ionic bond.
• Valence electrons- can be shared with other atoms
  in a chemical bond called a covalent bond.

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Atoms called Ions

• Atoms that have lost or gained electrons- to
  become more stable are called ions.
• Atoms that form ionic bonds are ions. This
  means that when they form a bond, they either
  give electrons- (and become more positive) or
  they take electrons- (and become more negative).

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Atoms called Isotopes

• Atoms of the same element with different numbers
  of neutrons0 are called isotopes.
• Atoms of the same element always have the same
  number of protons. They usually have the same
  number of neutrons0 but if they dont then one is
  an isotope.

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Modern View of Atoms

• Here is another model of the atom that is a more
  accurate than the Bohr atom, but more
  complicated.
• This shows circular shaped s orbitals along
  with teardrop shaped p orbitals.

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Questions

• How do we identify atoms of each element?
• What are the parts of each atom? Their charges?
  Where are they found?
• What is a valence electron? Why is it important?
• Which particles contribute most to an atoms
  mass? Which particles do not?
• Before an atom makes a bond, what is its charge?
  Why?
• What is an ion? Give an example.
• How does an atom become positive? Become
  negative?
• What is an isotope?