Atomic Theory and Structure
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Describe the composition of the atom and the experiments that led to that knowledge
Describe how Rutherford predicted the nucleus
Understand the inverse relationship between wavelength and frequency, and the direct relationship
between energy and frequency
Analyze diagrams related to the Bohr model of the hydrogen atom in terms of allowed, discrete energy
levels in the emission spectrum
Describe the electron cloud of the atom in terms of a probability model
Atomic Structure
Characterize the protons, neutrons, electrons: location, relative charge, relative mass (p=1, n=1,
e=1/2000).
Use symbols: A= mass number, Z=atomic number
Use notation for writing isotope symbols: 235
or U-235
92 U
Identify isotope using mass number and atomic number and relate to number of protons, neutrons and
electrons
Have a conceptual awareness of the nature of average atomic mass. (Relative abundance of each isotope
determines the average- no calculations)
Dalton’s Atomic Theory
Dalton
Matter is composed of very tiny or
microscopic particles called
“Atoms”. An indivisible particle which can never
be created nor destroyed.
Today, Modern
Atoms of an element are identical
in size, shape, mass, and in other
properties.
Atoms of different elements are
different in their properties.
Atoms combine with each other in small while
numbers.
Person
Democritus
Dalton
J. J. Thomson
Experiment
Rutherford
Bohr
Chadwick
Milliken
Newest Model =
Quantum Model
Gold Foil
Cathode ray tube
Oil Drop
Focus
“Atom”
Atomic Theory
Negative and positive regions, electrons exist
Small, positively charged center (nucleus)
Electrons in specific energy levels
neutron
Electron’s exact charge and mass
Electrons are in an electron cloud
1. What two things did Rutherford’s gold foil experiment tell us about the structure of the atom?
a. ____________________________________
b. _______________________________________
2. Draw the Bohr Model of the atom for sodium.
3. Distinguish between mass number and atomic number.
4. List the three major subatomic particles with charge, location, and approximate mass.
a. _____________________________________________
b. _____________________________________________
c. _____________________________________________
5. Why is there an average atomic mass on the periodic table?
6. The number of ______ determines the identity of an element and the number of ____
determines the particular isotope of the elemtent.
7. Complete the following table.
Hyphen
Element
# of
Mass #
notation
Protons
Hydrogen
C– 14
Carbon
14
19
Cl – 37
# of
Electrons
Atomic # of
Number Neutrons
Isotope, Ion,
or Neutral
neutral
3
neutral
Ion, isotope
18
8. Referring to the reference table for the Bohr Model of Hydrogen for the following questions
a) What color of visible light is associated with an electron moving from n = 6 to n =
2? ________________________________
b) What color of visible light is associated with an electron moving from n = 5 to n =
2?_______________________________
c) What color of visible light is associated with an electron moving from n = 3 to n =
2?_______________________________
d) Is the frequency of red light greater than the frequency of blue light? What is the
basic relationship between frequency and wavelength?
________________________________
e) The wavelength of visible light emitted by a material is measured at 4.86 x 10 -7m,
this can be associated with an electron changing from n = _____ to n = ______.
f) Is the frequency of electromagnetic radiation emitted when an electron moves
from n = 4 to n = 3 greater than the frequency of light emitted when an electron
moves from n = 4 to n = 1? ________________________________
g) Is blue light emitted or absorbed when an electron moves from n = 2 to n = 4?
________________________________
h) Is the energy of the electromagnetic radiation emitted when an electron moves
from n = 5 to n = 3 greater than the energy emitted when electron moves from n
= 3 to n = 1? ________________________________
9. Define the following terms used to explain the most modern model of the atom (Quantum
Mechanical Model).
a) Orbital ________________________________
b) electron cloud _____________________________
10. List the 4 types of orbitals and how many different orientations each can take.
a. ____________
b. ____________
c. ____________
d. ____________
11. How many electrons can occupy any one orientation of an orbital?___________
What rule is this?________
Multiple Choice
1. The atomic number of an atom is always equal to the total number of
(A) neutrons in the nucleus
(B) protons in the nucleus
(C) neutrons plus protons in the atom
(D) protons plus electrons in the atom
2. An atom that contains 35 protons, 45 neutrons, and 35 electrons has an atomic number of
(A) 35
(C) 80
(B) 45
(D) 115
3. Which atom has a nucleus that contains 13 protons and 14 neutrons?
(A) Mg
(C) Al
(B) Be
(D) N
4. What is the total number of electrons in a neutral atom of fluorine?
(A) 9
(C) 19
(B) 10
(D) 28
5. What is the mass number of an atom which contains 21 electrons, 21 protons, and 24 neutrons?
(A) 21
(C) 45
(B) 42
(D) 66
6. Which of the following particles has the least mass?
(A) an electron
(C) a hydrogen atom
(B) a proton
(D) a neutron
12
7. Compared to an atom of 6C, an atom of 146C has
(A) more protons
(C) more neutrons
(B) fewer protons
(D) fewer neutrons
8. The number of protons in an atom of 31H is
(A) 1
(C) 3
(B) 2
(D) 4
127
9. The nucleus of an atom of 53I contains
(A) 53 neutrons and 127 protons
(B) 53 protons and 127 neutrons
(C) 53 protons and 74 neutrons
(D) 53 protons and 74 electrons
10. The nucleus of an atom of K-42 contains
(A) 19 protons and 23 neutrons
(B) 19 protons and 42 neutrons
(C) 20 protons and 19 neutrons
(D) 23 protons and 19 neutrons
11. An experiment in which alpha particles were used to bombard thin sheets of gold foil led to the
conclusion that an atom is composed mostly of
(A) empty space and has a small, negatively charged nucleus
(B) empty space and has a small, positively charged nucleus
(C) a large, dense, positively charged nucleus
(D) a large, dense, negatively charged nucleus
12. Atoms of 16O, 17O, and 18O have the same number of
(A) neutrons, but a different number of protons
(B) protons, but a different number of neutrons
(C) protons, but a different number of electrons
(D) electrons, but a different number of protons
13. All the isotopes of a given atom have
(A) the same mass number and the same atomic number
(B) the same mass number but different atomic numbers
(C) different mass numbers but the same atomic number
(D) different mass numbers and different atomic numbers
14. If the nucleus of an atom is represented as 2411X, the atom is
(A) Na
(C) Mg
(B) Al
(D) Br
15. Which statement concerning elements is true?
(A) Different elements must have different numbers of isotopes.
(B) Different elements must have different numbers of neutrons.
(C) All atoms of a given element must have the same mass number.
(D) All atoms of a given element must have the same atomic number.
16. The atomic mass of an element is defined as the weighted average mass of that element’s
(A) most abundant isotope
(B) least abundant isotope
(C) naturally occurring isotopes
17. Which particle has approximately the same mass as a proton?
(A) alpha
(C) electron
(B) beta
(D) neutron
18. Experimental evidence indicates that the nucleus of an atom
(A) contains most of the mass of the atom
(B) contains a small percentage of the mass of the atom
(C) has no charge
(D) has a negative charge
19. Which subatomic particles have a mass of approximately 1 atomic mass unit each?
(A) proton and electron
(C) neutron and positron
(B) proton and neutron
(D) electron and positron
20. Which two atoms are isotopes?
(A) 146C and 147N
(C) 31H and 32He
(B) 2111Na and 2311Na (D) 73Li and 94Be