Atoms, Isotopes, and Ions

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Atoms, Isotopes, and Ions

• 4.3 4.7, 4.10, 4.11

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Atomic Theory

• In 1808 John Dalton proposed atomic theory.
• Daltons theory explained several laws known at
  the time.
• Law of conservation of matter
• Law of definite proportions
• Law of multiple proportions

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Daltons Atomic Theory (1808)

1. Elements are made of tiny particles called atoms.
2. Atoms of a given element are identical.
3. Atoms of different elements differ from each
   other in some fundamental way.

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Daltons Atomic Theory (1808)

• Atoms of one element can join with atoms of other
  elements to form compounds.
• A given compound is always made of the same
  elements combined in the same ways.
• Explains the law of multiple proportions and the
  law of definite composition.

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Daltons Atomic Theory (1808)

• Atoms are indivisible in chemical reactions.
• Chemical reactions change how atoms are grouped
  (bonded) together.
• Explains the law of conservation of matter.

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Atomic Theory

• Daltons proposal lead to much research as to the
  nature of the atom.
• In the late 1800s chemists/physicists determined
  that the atom is made up of smaller, subatomic,
  particles.

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Atomic Theory - 1910

• 1896, JJ Thomson demonstrated that atoms can
  emit negative particles.
• Called these particles electrons.
• Since atoms are neutral he also proposed that
  they must contain positive particles.
• These particles were not fully described/named
  until 1919.

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Atomic Theory - 1910

• 1910 Lord Kelvin proposed the plum pudding
  model of the atom.
• Proposed that electrons were scattered within a
  cloud/pudding of positive charge.

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Atomic Theory - 1911

• 1911 an experiment was conducted in Ernest
  Rutherfords lab that showed the plum pudding
  model to be incorrect.
• Experiment was conducted by Geiger and Marsden
  and the findings interpreted by Rutherford.
• See page 84

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The gold foil experiment

• What they did see board
• What they found see board
• What Rutherford concluded.

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Rutherfords Model of the Atom

• First to propose a nuclear atom.
• Rutherford proposed that
• the atom must have nearly all its mass, and
  positive charge, in a central nucleus about
  10,000 times smaller than the atom itself.
• Most of the atom is empty space and the electrons
  are scattered through out this empty space.

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A New Model of the Atom

• Expected based on
• Plum pudding model
• Rutherfords model
• Based on his results

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Subatomic Particles

• Rutherford continued to study the atom and the
  positive matter of the atom.
• 1919, particle named the proton
• 1932 James Chadwick proposed the existence of a
  third subatomic particle, the neutron.

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Subatomic Particles
Subatomic Particle Charge Mass, amu Location in atom
Electron (e-) -1 0 amu Outside of nucleus
Proton (p) 1 1 amu Nucleus
Neutron (n) 0 1 amu Nucleus
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Mass of Subatomic Particles

• Protons and neutrons have the same mass (in the
  range of 10 -24 g).
• Neutrons are slightly heavier.
• Mass is expressed in amu
• Atomic mass unit (amu) 1/12 the mass of a
  carbon-12 atom

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Mass of Subatomic Particles

• The mass of the electron is tiny as compared to
  that of the proton and neutron.
• Therefore, the electrons mass is considered to
  be 0 amu when calculating the mass of an atom.

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Subatomic Particles and the Elements

• Each element has a unique number of protons.
• Number of protons defines the element.

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Subatomic Particles and the Elements

• Since atoms are neutral, for every proton there
  is a/n _________.
• When atoms interact to form compounds, it is
  their ___________ that intermingle.

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Terms

• Atomic number number of protons in an atom
• Also indicates the number of electrons in the
  atom.
• Finding atomic number on the periodic table.

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Terms

• Mass number sum of the of protons and the
  neutrons in the nucleus of an atom
• FOR MOST ELEMENTS THE MASS NUMBER IF NOT ON THE
  PERIODIC TABLE.
• You will be given enough information to determine
  mass number or number of neutrons.

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Terms

• Isotopes atoms of a given element that differ
  in mass number
• Isotopes have the same number of _____________.
• Isotopes differ in the number of _______.

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Isotopes

• Writing atomic symbols for isotopes
• See board and pg 87

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FAQ - Isotopes

• When is mass number found on the periodic table?
• Whats the atomic mass? Is it the same as the
  mass number?

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Practice

• Start 42 on page 110.

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Ion Formation

• Ions are formed when atoms gain or lose
  electrons.
• Proton and neutron number are unchanged when an
  ion forms.

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Ions - Terms

• Ion charged atom or group of atoms
• Cation positively charged ion
• Metals form cations.
• Anion negatively charged ion
• Nonmetals form anions.

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Ions

• Na atom
• _____ protons _____ electrons
• Na ion
• _____ protons _____ electrons
• Name of ion sodium ion

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Ions

• Calcium atom
• _____ protons _____ electrons
• Ca 2 ion
• _____ protons _____ electrons
• Name of ion calcium ion

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Ions

• Sulfur atom
• _____ protons _____ electrons
• S2- ion
• _____ protons _____ electrons
• Name of ion sulfide ion

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Ion Charge and the Periodic Table
Group Ion Charge e- lost/gained
I A 1 1 e- lost
II A 2 2 e- lost
III A metals 3 3 e- lost
V A nonmetals 3- 3 e- gained
VI A nonmetals 2- 2 e- gained
VII A 1- 1 e- gained
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Naming Ions

• Name of a monatomic cation is the name of the
  element
• Examples
• Ca 2 calcium ion
• Al 3 aluminum ion
• K

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Naming Ions

• Monatomic anions are named by changing end of the
  name of the element to ide
• Example S2- sulfide ion

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Naming Ions

• You need to know
• N3- nitride ion
• P3- phosphide ion
• O2- oxide ion
• S2- sulfide ion
• F- fluoride ion
• Cl - chloride ion
• Br- bromide ion
• I- iodide ion

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Ionic Compounds

• Structure
• In an ionic compound there is a regular
  arrangement of oppositely charged particles.
• Ions are arranged in a 3-D crystalline structure
  that maximizes attractive forces and minimizes
  repulsive forces.
• Also called a lattice structure
• See page 102

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Ionic Compounds

• Physical Properties all are related to the
  structure of the compounds
• Solids at room temperature
• Relatively high melting and boiling points
• No vapor pressure
• Meaning they dont evaporate
• Electrolytes
• Conduct electricity when melted or dissolved in
  water

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Ionic Compounds

• The chemical formula for an ionic compound
  represents the lowest, whole number ratio of the
  component ions that has a net charge of zero.
• Total positive charge total negative charge

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Ionic Compounds

• Name the compound by naming the ions.

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Ionic Compounds

• Writing formulas for and naming binary ionic
  compounds
• Magnesium oxide

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Ionic Compounds

• Magnesium oxide
• The formula is the simplest ratio of ions that
  have a net charge of zero.
• Ions present Mg2 and O2-
• Formula

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Ionic Compounds

• Magnesium chloride
• The formula is the simplest ratio of ions that
  have a net charge of zero.
• Ions present Mg2 and _____
• Formula

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Ionic Compounds

• Practice
• Note we are currently applying the content of
  4.11 and 5.2 (type I binary ionic compounds)

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Types I Binary Compounds

• Compound between a metal and a nonmetal
• Metal forms only one ion
• Name the cation and then the anion.
• Name of the cation is the name of the element
• Name of the anion is the name of the nonmetal
  with the ending changed to ide

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Monoatomic cations to know
Group Charge on ion examples
IA 1 Na1 sodium (ion) K1 potassium (ion)
IIA 2 Mg2 magnesium (ion)
IIIA metals 3 Al3 aluminum (ion)
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Monoatomic anions to know
Group Charge on ion examples
VA -3 N3- nitride (ion) P3- phosphide (ion)
VIA -2 O2- oxide (ion) S2- sulfide
VIIA -1 F1- fluoride (ion) Cl1- chloride (ion) Br1- bromide (ion) I1- iodide (ion)
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Practice

• Name ? chemical formula
• Chemical formula ? name