Chapter 4 Notes - ms. Herberholz's class website · Chapter 4 Notes 1 CHAPTER 4 Atomic Structure...
Transcript of Chapter 4 Notes - ms. Herberholz's class website · Chapter 4 Notes 1 CHAPTER 4 Atomic Structure...
Chapter 4 Notes
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CHAPTER 4Atomic Structure
4.1 Atoms• Democritus first suggested the
idea of atoms• Indivisible & Indestructible• 460 B.C. – 370 B.C.
Dalton’s Atomic Theory
1. All elements are composed of submicroscopic indivisible particles called atoms
2. Atoms of the same element are identical. The atoms of any one element are different from those of any other element.
• Every sodium atom in the universe is the same…
• Every magnesium atom in the universe is thesame…
3. Atoms of different elements can physically mix together or can chemically combine with one another in simple wholenumber ratios to form compounds.
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4. Chemical reactions occur when atoms are separated, joined, or rearranged. However, atoms of one element are never changed into atoms of another element as a result of a chemical reaction.
• Protons
• Electrons
• Neutrons
Parts of an atom
Do not have unique properties!
Atom• The smallest particle of an element that
retains the properties of that element.• Have a size ranging from:(5 x 1011m) – (2 x 1010m)
• The protons, electrons, and neutrons in one atom are the same as in any other atom.
• The number of protons, electrons, and neutrons is what makes each atom unique.
Scanning Tunneling MicroscopeVisualizes
individual atoms and makes it possible to see them as a 3D image on a monitor.
Atoms of Copper and Iron
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4.2 The Structure of the Nuclear AtomAtoms can be broken down into more fundamental particles.
In Chemistry we will learn about protons, electrons, and neutrons.
Electrons• Negatively charged subatomic particle• 1/1840 the mass of 1 proton• Millikan: discovered that an electron
carries one unit of negative charge
Electrons• Discovered by Thomson using the Cathode
ray tube experiment
Electrons being repelled by magnet... Protons• Positively charged subatomic
particles• Carries a one positive charge
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Neutrons• Subatomic particle with no charge• Discovered by Chadwick• Mass equals that of a proton
The Atomic Nucleus• The central core of an atom, composed of protons and neutrons
• Responsible for almost all the mass of an atom
ProtonsNeutrons
• The nucleus has a positive charge, and it occupies a very small part of the volume of an atom.
Nucleus & Energy Levels
ProtonNeutron
Nucleus• 99.99% of the mass of an atom• Contains Protons and Neutrons• Overall positive charge• Very little volume of the atom• Proton Number defines the atom
Energy Level• Contains only electrons• 0% of the mass of an atom• Overall negative charge• Most of the volume of an atom• Determines the properties of an atom
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• The negatively charged electrons in an atom occupy most of the volume of the atom.
The Rutherford atomic model is known as the nuclear atom.
• The protons are located in the nucleus• The electrons are around the nucleus• The electrons occupy most of the volume of the atom
Electrons: determine the properties of every atoms.
Protons: define what each atoms is.
4.3 Atomic Number
• How are atoms of one element different from those of another element?
• Differences among elements result from differences in the numbers of protons in their atoms.
Atomic Number• The number of protons in the nucleus of the atom
of that element.
• Example: The atomic number of Oxygen is 8
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• Remember that atoms are electrically neutral. Thus the number of protons in the nucleus of an atom must equal the number of electrons around its nucleus.
• The periodic table gives the atomic number of each element.
Nucleons: protons & neutrons because they are in the nucleus.s, p, d, f: subshells where electrons are found
Mass Number
• Mass number is the total number of protons and neutrons in the nucleus of an atom.
• You can determine the composition of an atom of any element from its atomic number and its mass number.
Example:• Beryllium: atomic number 4 mass number 9# p = 4 # e = 4 # n = 5
Aluminum Al Palladium Pd Atomic Number = Atomic Number =
Mass Number = Mass Number =
Proton Number = Proton Number =
Electron Number = Electron Number=
Neutron Number= Neutron Number =
Mass of Electrons = Mass of Electrons =
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Shorthand Notation• The atomic number is written as a subscript. The mass number is written as a superscript.
• Example: Be Al
Al
9
4
27
13
What can change in an atom?
• Protons: can never change• Electrons: if the number changes, then an ion forms.
• Neutrons: if the number changes, then an isotope forms.
If the proton number changes….
• Then the entire atom changes.• If oxygen gains a proton, it becomes fluorine.
• If oxygen loses a proton, it becomes nitrogen.
If the neutron number changes….
• Then a different version of the same atom forms.
• Oxygen16 has 8 neutrons.• Oxygen17 has 9 neutrons.• Oxygen18 has 10 neutrons
Isotopes of Elements• The nuclei of the atoms of a given element must all contain the same number of protons, but the number of neutrons may vary.
Isotopes vs. AllotropesIsotopes: atoms of the same element with different numbers of neutronsAllotropes: different forms of an element, usually when the same atoms are joined as compound.
Carbon exhibits both…• Isotopes: Carbon12, Carbon13, Carbon14• Allotropes: graphite, diamond, and fullerenes
The way atoms are arranged
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Isotopes• Atoms that have the same number of protons but different numbers of neutrons
• Because isotopes of an element have different numbers of neutrons, they also have different mass numbers.
• Isotopes are chemically alike because they have identical numbers of protons and electrons.
Hydrogen• Hydrogen has three known isotopes:
• Hydrogen1 (one proton, no neutrons)• Protium• Hydrogen2 (one proton, one neutron)• Deuterium• Hydrogen3 (one proton, two neutrons)• Tritium
Atomic Mass• The masses of atoms are too small to work with so we use Carbon as the comparative atom.
• An Atomic Mass Unit (amu) is defined as onetwelfth the mass of a carbon12 atom.
• Proton=1amu, Neutron=1amu, electrons=0amu
Atomic Mass• The atomic mass of an element is a
weighted average mass of the atoms in a naturally occurring sample of the element.
Atomic Mass vs. Mass Number
• There is a difference!!• Average Atomic Mass is the mass on
the periodic Table• Mass Number is the actual mass of a
given atom.
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• The weighted average mass reflects both the mass and the relative abundance of the isotopes as they occur in nature.Chlorine35 Chlorine36(54%) (46%)
Isotopes
Relative Abundance
Calculating the Atomic Mass of an Element
You must know:• The number of stable isotopes of that element• The mass of each isotope• The natural percent abundance of each isotope
Average Atomic Mass of Carbon
• Carbon12: 12 x 0.917 = 11.004• Carbon13: 13 x 0.069 = 0.897• Carbon14: 14 x 0.014 = 0.196
• Add together products together
• 12.097 (Avg. atomic mass)
Determining Average Atomic Mass of a "New" element
Isotope Percentage Show Work Fontainium 41 87.3 %
Fontainium 43 9.8 %
Fontainium 44 2.9 %
Average Atomic Mass
Write the following in shorthand notation...
Oxygen 15
Oxygen 16
Oxygen 17
Isotope or Common
Isotope or Common
Isotope or Common
States of AtomsGround State: electrons are at their lowest possible energy level
Excited State: electrons have absorbed energy and jumped to a higher energy level
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Nucleus
Energy Levels of an Atom If an atom gains electrons, then….
• Then a negatively charged version of the same atom forms.
• If oxygen gains 2 electrons, it has 10 electrons and 8 protons.
• It now has a “2” charge
If an atom loses electrons, then….
• Then a positively charged version of the same atom forms.
• If calcium lost 2 electrons, it has 18 electrons and 20 protons.
• It now has a “2+” charge.
Examples of IonsSulfur Magnesium Lithium Chlorine
Neutral Version
P=16 P=12 P=3 P=17
E=16 E=12 E=3 E=17
Gain or Loss
Gain 2 electrons
Lose 2 electrons
Lose 1 electron
Gain 1 electron
New electron number E=18 E=10 E=2 E=18
Charge S2 Mg 2+ Li + Cl
Cation vs. Anion• Cation: Positive Ion
More protons than electrons I am “Positive” I love my Cat.• Anion: Negative Ion
More electrons than protons
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AtomicNumber Protons Electrons Neutrons Mass
Number
Al 3+
Hydrogen – 1
Hydrogen – 3
H +
Oxygen – 16
Oxygen – 14
O 2
AtomicNumber Protons Electrons Neutrons Mass
Number
Al 3+ 13 13 10 14 27
Hydrogen – 1 1 1 1 0 1
Hydrogen – 3 1 1 1 2 3
H + 1 1 0 0 1
Oxygen – 16 8 8 8 8 16
Oxygen – 14 8 8 8 6 14
O 2 8 8 10 8 16
Element Atomic # ProtonsNumber
ElectronNumber
NeutronNumber
MassNumber
Ion, Isotope, or Neutral
Fluorine 9 9 9 10 19
Chromium 24 24 24 32 56
Calcium 20 20 18 20 40
Iodine 53 53 54 74 127
Polonium 84 84 84 131 215
Neutral = Periodic Table VersionElement Atomic
#ProtonsNumber
ElectronNumber
NeutronNumber
MassNumber
Ion, Isotope, or Neutral
Fluorine 9 9 9 10 19 Neutral &Common
Chromium 24 24 24 32 56 Isotope
Calcium 20 20 18 20 40 Cation
Iodine 53 53 54 74 127 Anion
Polonium 84 84 84 131 215 Isotope
The Periodic Table: A Preview
• The Periodic Table allows you to compare properties of one elementto another element
• Period• Group