1. Atom 2. Proton 3. Nucleus 4. Neutron 5. Electron 6. Mass number 7. Atomic number 8. Atomic mass unit 9. Isotope 10. Atomic Mass Due Tomorrow! Atomic Theory Unit Vocabulary • First column: words • Second column: definition from text • Third column: definition in your own words • Fourth column: Picture or example
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1. Atom 2. Proton 3. Nucleus 4. Neutron 5. Electron 6. Mass number 7. Atomic number 8. Atomic mass unit 9. Isotope 10. Atomic Mass Due Tomorrow! First.
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1. Atom2. Proton3. Nucleus4. Neutron5. Electron6. Mass number7. Atomic number8. Atomic mass unit9. Isotope
10. Atomic Mass Due Tomorrow!
Atomic Theory Unit Vocabulary• First column:
words• Second column:
definition from text• Third column:
definition in your own words
• Fourth column: Picture or example
SC3. Students will use the modern atomic theory to explain
characteristics of atoms.
“Atomic Theory and Structure”
OBJECTIVES:Explain Dalton’s atomic theory.Identify the parts of an atom,
their location, charge, and relative mass.
Determine the numbers of subatomic particles in an atom.
Democritus’s Atomic Philosophy
Democritus- all matter is made up of imperishable, indivisible units, which
he called atoma.
Dalton’s Atomic Theory
1)All elements are composed of atoms.
2) Atoms of the same element are identical. Atoms of different elements are different.
John Dalton(1766 – 1844)
3)Atoms of different elements can combine to form compounds.
4) In chemical reactions, atoms are combined, separated, or rearranged, but never changed into atoms of another element.
Modern Theory
One change to Dalton’s atomic theory is that atoms are divisible into subatomic particles:
ElectronsProtons Neutrons
The Subatomic Particles
Location ChargeRelative
mass in amu Function
Proton
Neutrons
Electrons 0.00055 amu
amu: mass of 1/12 of a carbon atom
Atom Math
Atomic number: number of protons (and electrons IF atom is neutral)Atomic mass:
called mass number when rounded to nearest whole number. Mass Number equals protons + neutrons.
Atom Math Protons: atomic number Electrons: same as protons if atom is
is called an ion. The number of electrons lost or gained is indicated by a charge.
Element
Protons Electrons
Ion
Oxygen Gains 2 electrons
Aluminum Loses 3 electrons
Beryllium Loses 2 electrons
Bromine Gains 1 electron
Assignment
Ion Practice Set
Finish for homework
Ion Review
Element
Number of protons
Number of Electrons
Ion
Sulfur Gains 2 electrons
Sodium Loses 1 electron
Boron loses 3 electrons
Atomic StructurePart 2“Isotopes and Ions”
Isotopes
Atoms of the same element can have different numbers of neutrons.
Thus, different mass numbers.
Naming Isotopes To distinguish between isotopes of the same
element, put the mass number after the name of the element:
AZ Proton
sNeutro
nsOxygen-18
Aluminum-2510Be (beryllium-10)
79 Br (bromine-79)
Potassium-41
X
IsotopesElements occur in nature as mixtures of isotopes.
So, atoms of the same element aren’t necessarily the same….AVERAGE atomic mass
Isotope ReviewProtons Neutrons
Carbon-12
Carbon-14
Uranium-238
Uranium-235
Hydrogen-1
Hydrogen-2
Hydrogen-3
Work Session
Complete Ion Practice Set and Isotope Practice Sets (15 minutes)
Percent Abundance and Average Atomic
Mass
Atomic Mass The average atomic mass: is based on
the abundance (percentage) of each variety of that element in nature.
Lesson Preview
Argon has three naturally occurring isotopes: argon-36, argon-38, and argon-40. Based on argon’s reported atomic mass, which isotope do you think is the most abundant in nature?
Poll everywhere response
To calculate the average atomic mass:
Multiply the atomic mass of each isotope by it’s
abundance percentage (expressed as a decimal),
then add the results.
Atomic Masses
Isotope Atomic mass
% in nature
Carbon-12 98.89%
Carbon-13 1.11%
Carbon-14 <0.01%negligible
Atomic mass is the average of all the naturally occurring isotopes of that element.
Carbon = 12.011
Average Atomic Mass
Rubidium has two common isotopes, Rb-85 and Rb-87. If the abundance of Rb-85 is 72.2% and the abundance of Rb-87 is 27.8%, what is the average atomic mass of rubidium?