Atomic Theory and Structure

·  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: or U-235

·  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 / Today, Modern

Matter is composed of very tiny or

microscopic particles called
“Atoms”. An indivisible particle which can never be created nor destroyed.

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 / Experiment / Focus
Democritus / “Atom”
Dalton / Atomic Theory
J. J. Thomson / Cathode ray tube / Negative and positive regions, electrons exist
Rutherford / Gold Foil / Small, positively charged center (nucleus)
Bohr / Electrons in specific energy levels
Chadwick / neutron
Milliken / Oil Drop / Electron’s exact charge and mass
Newest Model = Quantum Model / 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 notation / Element / # of Protons / Mass # / # of Electrons / Atomic Number / # of Neutrons / Isotope, Ion, or Neutral
Hydrogen / neutral
C– 14 / Carbon / 14
19 / 18
3 / neutral
Cl – 37 / Ion, isotope

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

7.  Compared to an atom of 126C, 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

9.  The nucleus of an atom of 12753I 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