Chapter 3 Review1

1
Chapter 3 Review-1

• The basic principles of atomic theory that are
  still recognized today were first conceived by
  John Dalton.
• If 4 grams of element A combine with 10 grams of
  element B, then 12 grams of element A will
  combine with 30 grams of element B.
• Dalton's atomic theory helped to explain the law
  of conservation of mass because it stated that
  matter could not be created or destroyed.
• The law of multiple proportions was proposed by
  John Dalton.
• The rays produced in a cathode tube in early
  experiments were deflected away from a negative
  plate.
• Millikan's experiments with the electron showed
  that the electron carried the smallest possible
  negative charge.

2
Chapter 3 Review-2

• In Rutherford's experiment, a very few of the
  positively-charged particles were greatly
  deflected as they passed through the metal.
• The mass of the neutron is about the same as
  that of a proton.
• Most of the volume of an atom is made up of the
  electron cloud.
• The hydrogen isotope with the LOWEST mass is
  named or called protium.
• The hydrogen isotope with the HIGHEST mass is
  named or called tritium.
• Atoms of the same element can differ in mass
  number, BUT NEVER in their atomic number.
• The relative masses of all atoms are based on the
  mass of one atom of carbon-12 isotope being equal
  to 12 mass units.

3
Chapter 3 Review-3

• Neon has an atomic number of 10. Calcium has an
  atomic number of 20. Compared to a mole of neon,
  a mole of calcium contains the same number of
  atoms. (6.022 x 1023 atoms)
• All atoms of the same element have the same
  number of protons and electrons.
• Aluminum-28 has as atomic number of 13. How many
  neutrons does this isotope have? 15
  (28-1315)
• Carbon-12 has 6 neutrons. What is the atomic
  number of carbon-12? Atomic number 6 amu
• Sulfur has an atomic number of 16. What is the
  mass number of the isotope contain 15 neutrons?
  31 (16 protons 15 neutrons)
• As the mass number of the isotopes of a
  particular element increases, the number of
  protons remains the same.

4
Chapter 3 Review-4

• Phosphorus-32 has an atomic number of 15. How
  many neutrons does this isotope have? 17
  (32-15 17 neutrons).
• Silicon-31 contains 14 protons. How many
  electrons does an atom of silicon 31 contain?
  14 electrons (protonselectrons).
• The smallest particle of an element that can
  exist either alone or in combination with the
  smallest such particles of elements is called an
  atom.
• The negatively charged subatomic particles that
  surround or orbit the nucleus are called
  electrons.
• The short-range attractive forces that hold the
  nuclear particles together are called nuclear
  forces.
• Atoms of the same element that have different
  masses are called isotopes and nuclides.

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Chapter 3 Review-5

• The number of protons in the nuclei of the atoms
  of a particular element is referred to as the
  atomic number.
• The weighted average of the atomic masses of the
  naturally occurring isotopes of an element is
  referred to as average atomic mass.
• The amount of a substance that contains a number
  of particles equal to the number of atoms in
  exactly 12 g in a carbon- 12 is referred to as a
  mole.
• The mass in grams of one mole of an element in a
  compound is referred to as the molar mass of the
  atom.
• The electrically neutral, subatomic particles
  found in the nuclei of atoms are called neutrons.
• ALL sub-atomic particles found in the nucleus of
  an atom are called nucleons.

6
Weighted Average Problem

• U-234 percentage of occurrence ( 0.005 ),amu
  234.041
• U-235 percentage of occurrence ( 0.720 ),amu
  235.043
• U-238 percentage of occurrence ( 99.275
  ),amu 238.051

(mass number x decimal of occurrence) (mass
number x decimal of occurrence) (mass number x
decimal of occurrence) weighted average
atomic mass
Solution (0.00005 x 234.041) (0.0072 x
235.043) (.99275 x 238.051) (0.00117)
(1.692)
(236.325) 238.018 amu
7
Atomic Chart
8
Short Essay Questions

• A. Know the Five major proposals of Dalton's
  theory
• All matter is made up of extremely small
  particles called atoms.
• Atoms of the same type of matter are identical in
  size, mass and other properties.
• Atoms can not be broken down into smaller
  particles, or be created or destroyed.
• Atoms of unlike elements combine in simple whole
  number ratios to form chemical compounds.
• In chemical reactions, atoms are combined,
  rearranged or separated.

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Short Essay Question 2

• List, define and describe the three subatomic
  particles that make up the atom.
• Electrons negatively charged, very light mass
  1/1840th of a proton orbit the nucleus, most of
  the volume of the atom comes from the electron
  cloud.
• Protons positively charged, located in the
  nucleus, identifies the type of atom, contributes
  to the mass of the atom about equal in mass to a
  neutron.
• Neutrons no charge located in the nucleus,
  contributes to the mass of the atom responsible
  for radioactivity and isotopes.