unit 1 exam: atomic structure & history
name ______________________ date ____________

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. what is the atomic number of an element whose atoms each contain 47 protons, 60 neutrons, and 47 electrons?
a. 13 b. 47 c. 60 d. 107

3. which two particles have approximately the same mass?
a. neutrons and electrons
b. neutrons and protons
c. protons and electrons
d. protons and neutrons

4. if the nucleus of an atom is represented as $^{27}_{13}\text{x}$, the atom is
a. na b. al c. mg d. be

5. an experiment using alpha particles to bombard a thin sheet of gold foil indicated that most of the volume of the atom is left is taken up by
a. electrons b. protons
c. neutrons d. empty space

6. which particle has a mass of approximately one atomic mass unit and a unit positive charge?
a. a neutron b. a proton
c. a beta particle d. an alpha particle

7. the number of protons in an atom of $^3_1\text{h}$ is
a. 1 b. 2 c. 3 d. 4

8. which particle is electrically neutral?
a. proton b. positron
c. neutron d. electron

9. which of the following particles has the lowest mass?
a. proton b. hydrogen nucleus
c. neutron d. electron

10. which statement best describes an electron?
a. it has a smaller mass than a proton and a negative charge.
b. it has a smaller mass than a proton and a positive charge.
c. it has a greater mass than a proton and a negative charge.
d. it has a greater mass than a proton and a positive charge.

Question

unit 1 exam: atomic structure & history
name ______________________ date ____________

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. what is the atomic number of an element whose atoms each contain 47 protons, 60 neutrons, and 47 electrons?
   a. 13  b. 47  c. 60  d. 107

3. which two particles have approximately the same mass?
   a. neutrons and electrons
   b. neutrons and protons
   c. protons and electrons
   d. protons and neutrons

4. if the nucleus of an atom is represented as $^{27}_{13}\text{x}$, the atom is
   a. na  b. al  c. mg  d. be

5. an experiment using alpha particles to bombard a thin sheet of gold foil indicated that most of the volume of the atom is left is taken up by
   a. electrons  b. protons
   c. neutrons  d. empty space

6. which particle has a mass of approximately one atomic mass unit and a unit positive charge?
   a. a neutron  b. a proton
   c. a beta particle  d. an alpha particle

7. the number of protons in an atom of $^3_1\text{h}$ is
   a. 1  b. 2  c. 3  d. 4

8. which particle is electrically neutral?
   a. proton  b. positron
   c. neutron  d. electron

9. which of the following particles has the lowest mass?
   a. proton  b. hydrogen nucleus
   c. neutron  d. electron

10. which statement best describes an electron?
    a. it has a smaller mass than a proton and a negative charge.
    b. it has a smaller mass than a proton and a positive charge.
    c. it has a greater mass than a proton and a negative charge.
    d. it has a greater mass than a proton and a positive charge.

Accepted Answer

### Question 1
# Brief Explanations:
Atomic number is defined as the number of protons in the nucleus of an atom. So we check the options: A is neutrons (wrong), B is protons in nucleus (correct), C is neutrons + protons (mass number, wrong), D is protons + electrons (electrons don't determine atomic number, wrong).
# Answer: B. protons in the nucleus

### Question 2
# Brief Explanations:
Atomic number is the number of protons. The atom has 47 protons, so atomic number is 47.
# Answer: B. 47

### Question 3
# Brief Explanations:
Protons and neutrons have approximately the same mass (both ~1 atomic mass unit), while electrons have much less mass. So option C (proton and neutron) is correct.
# Answer: C. proton and neutron

### Question 4
# Brief Explanations:
The symbol $_Z^A X$ has $Z$ as atomic number (protons) and $A$ as mass number (protons + neutrons). Here $Z = 11$, $A = 23$. Atomic number 11 is sodium (Na).
# Answer: A. Na

### Question 5
# Brief Explanations:
Rutherford's gold foil experiment showed most of the atom's volume is empty space (alpha particles mostly passed through, few deflected). So the answer is D.
# Answer: D. empty space

### Question 6
# Brief Explanations:
Proton has mass ~1 amu and positive charge. Neutron has no charge, beta is electron (negative, small mass), alpha is 2 protons + 2 neutrons (mass ~4 amu). So B (proton) is correct.
# Answer: B. a proton

### Question 7
# Brief Explanations:
For $_Z^A X$ (here $^3_1$H), $Z$ (atomic number) is number of protons. So $Z = 1$, protons = 1.
# Answer: A. 1

### Question 8
# Brief Explanations:
Neutron has no charge (electrically neutral). Proton positive, positron positive, electron negative. So C (neutron) is correct.
# Answer: C. neutron

### Question 9
# Brief Explanations:
Electron has much less mass than proton, neutron, or hydrogen nucleus (which has a proton, mass ~1 amu). So electron (D) has lowest mass.
# Answer: D. electron

### Question 10
# Brief Explanations:
Electron has negative charge and much smaller mass than proton (proton ~1 amu, electron ~1/1836 amu). So option A (smaller mass than proton, negative charge) is correct.
# Answer: A. It has a smaller mass than a proton and a negative charge.

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