ATOMIC CONCEPTS
Regents Review
REGENTS REVIEW
1. A neutron has approximately the same
mass as a
A)
B)
C)
D)

An alpha particle
A beta particle
An electron
A proton
Correct Answer: Option D - A proton
REGENTS REVIEW
2. Which atom contains exactly 15 protons?
A)
B)
C)
D)


P-32
S-32
O-15
N-15
Correct Answer: Option A - P-32
The 32 is the weight of that isotope. The number of
protons is always the atomic number (An atom with
15 protons also has an atomic number of 15) So if you
take the isotope number (32) and subtract the proton
number (15) you get the number of neutrons for that
isotope. (17).
REGENTS REVIEW
3. When electrons in an atom in an excited
state fall to lower energy levels, energy is
A) Absorbed, only
B) Released, only
C) Neither released nor absorbed
D) Both released and absorbed
Correct Answer: Option B - Released, only
 The ground state is the lowest energy state. To
raise the atom to an excited state, energy must
be added. To fall back to the ground state (lowest
energy), the energy it had absorbed must be
released in the form of light or radiation.

REGENTS REVIEW
4. What is the mass number of an atom which contains 28
protons, 28 electrons, and 34 neutrons?
A) 28
B) 62
C) 56
D) 90


Correct Answer: Option - B - 62
The atomic number is equal to the number of protons in an
atom's nucleus. The atomic number is the number of protons
in an atom of an element. By definition, atoms have no overall
electrical charge. That means that there must be a balance
between the positively charged protons and the negatively
charged electrons. Atoms must have equal numbers of protons
and electrons. Atomic mass is found by adding protons plus
neutrons. 28 + 34 = 62. Electrons have a mass of nearly 0 so
they are not counted in the formula for atomic mass.
REGENTS REVIEW
5. Atoms of the same element that have different
numbers of neutrons are classified as:
A) Isotopes
B) Charged atoms
C) Isomers
D) Charged nuclei


Correct Answer: Option A - Isotopes
Atoms of the same element can have different
numbers of neutrons; the different possible versions
of each element are called isotopes. For example, the
most common isotope of hydrogen has no neutrons at
all; there's also a hydrogen isotope called deuterium,
with one neutron, and another, tritium, with two
neutrons.
REGENTS REVIEW
6. Which symbols represent atoms that are
isotopes?
A) C-14 and N-14
B) O-16 and O-18
C) Rn-222 and Ra-222
D) I-131 and I-131


Correct Answer: Option D - I-131 and I-131
Isotopes are atoms of the same element with same
atomic number but, with a different number of
neutrons (different atomic mass). Hence, only option
D is correct.
REGENTS REVIEW
7. Compared to the charge and mass of a proton,
an electron has
A) The same charge and a smaller mass
B) The same charge and the same mass
C) An opposite charge and a smaller mass
D) An opposite charge and the same mass


Correct Answer: Option C - An opposite charge
and a smaller mass
Protons are positively charged and electrons are
negatively charged. An electron has a mass that is
approximately 1843 times less than that of the
proton. The proton is a subatomic particle with an
electric charge of +1 elementary charge.
REGENTS REVIEW
8. Compared to an electron in the first electron shell of
an atom, an electron in the third shell of the same
atom has:
A) Less mass
B) More mass
C) Less energy
D) More energy


Correct Answer: Option D - More energy
Electron shells in an atom are orbits in which electrons
move around the nucleus. The closer orbit more tightly
bound are the electrons and lesser is the energy they
posses for reactions. As the electrons move farther from the
nucleus they are less bound to the nucleus and have higher
energy available for reaction.
REGENTS REVIEW
9. What is the atomic number, of an ion with 5 protons,
6 neutrons, and a charge of 3+?
A) 5
B) 6
C) 8
D) 11


Correct Answer: Option A - 5
The number of protons in the nucleus of an atom is known
as the atomic number, which determines the chemical
element to which the atom belongs. The chemical
properties of each atom are determined by the number of
(negatively charged) electrons, which for neutral atoms is
equal to the number of (positive) protons so that the total
charge is zero. There are 5 protons so the atomic number is
also 5. The charge of an atom is not involved in arriving at
the atomic number of that atom.
REGENTS REVIEW
10. In which group do the particles contain
only nucleons?
A)
B)
C)
D)

Protons and electrons
Neutrons and electrons
Protons and neutrons
Protons, neutrons, and electrons
Correct Answer: Option C - Protons and
neutrons
REGENTS REVIEW
11. What is the electron configuration of a
sulfur atom in the ground state?
A)
B)
C)
D)

2-4
2-8-4
2-6
2-8-6
Correct Answer: Option D - 2-8-6
REGENTS REVIEW
12. Which element's ionic radius is smaller than
its atomic radius?
A) Neon
B) Sodium
C) Nitrogen
D) Sulfur


Correct Answer: Option B - Sodium
Elements that lose electrons form positive ions that
are smaller than atoms of the same element.
Therefore the ionic radius of these ions is smaller
than its atomic radius. Only option B, sodium, is a
metal that will lose electrons.
REGENTS REVIEW
13. What is the total number of neutrons in an atom
of 5726Fe?
A) 26
B) 57
C) 31
D) 83




Correct Answer: Option C - 31
The atomic mass being 56 is the sum of the protons and
neutrons of the nucleus = 57
The atomic number (number of protons) in the nucleus = 26
Number of neutrons = Atomic mass - Atomic number = 57 26 = 31
REGENTS REVIEW
14. In which shell are the valence electrons of the
elements in Period 2 found?
A) 1
B) 2
C) 3
D) 4


Correct Answer: Option B - 2
Valence electrons are the electrons contained in the
outermost, or valence, electron shell of an atom. Valence
electrons are important in determining how an element reacts
chemically with other elements: The fewer valence electrons
an atom holds the less stable it becomes and the more likely it
is to react. The reverse is also true, the more full/complete the
valence shell is with valence electrons, the more inert an atom
is and the less likely it is to chemically react with other
chemical elements or with chemical elements of its own type.
REGENTS REVIEW
15. How many electrons are in the outermost
principal energy level of an atom of carbon
in the ground state?
A) 6
B) 2
C) 3
D) 4
Correct Answer: Option D - 4
 The electronic configuration of carbon in the
ground state is:

REGENTS REVIEW
16. When alpha particles are used to bombard
gold foil, most of the alpha particles pass
through undeflected. This result indicates that
most of the volume of a gold atom consists of:
A) Deuterons
B) Neutrons
C) Protons
D) Unoccupied space


Correct Answer: Option D - Unoccupied space
Because most of the particles do not hit anything
(pass right through), one can infer the atom is mostly
empty space.
REGENTS REVIEW
17. The elements in Period 3 all contain the
same number of
A)
B)
C)
D)

Occupied principal energy levels
Protons
Neutrons
Valence electrons
Correct Answer: Option A - Occupied
principal energy levels
REGENTS REVIEW
18. Which statement about the mass of an
electron is correct?
A) The mass of an electron is equal to the mass of
a proton.
B) The mass of an electron is less than the mass
of a proton.
C) The mass of an electron is equal to the mass of
a neutron.
D) The mass of an electron is greater than the
mass of a neutron.

Correct Answer: Option B - The mass of an
electron is less than the mass of a proton.
REGENTS REVIEW
19. What is the atomic number of an element that has
six protons and eight neutrons?
A) 8
B) 10
C) 6
D) 14


Correct Answer: Option C - 6
The atomic number (also known as the proton number) is
the number of protons found in the nucleus of an atom and
therefore identical to the charge number of the nucleus. It
is conventionally represented by the symbol Z. The atomic
number uniquely identifies a chemical element. In an atom
of neutral charge, atomic number is equal to the number of
electrons.
REGENTS REVIEW
21. An atom is electrically neutral because
A) Number of protons equals the number of
electrons
B) Number of protons equals the number of
neutrons
C) Ratio of the number of neutrons to the number
of electrons is 1:1
D) Ratio of the number of neutrons to the number
of protons is 2:1

Correct Answer: Option A - Number of
protons equals the number of electrons
REGENTS REVIEW
22. Atoms of which element have the greatest
tendency to gain electrons?
A)
B)
C)
D)

Bromine
Fluorine
Chlorine
Iodine
Correct Answer: Option B - Fluorine
REGENTS REVIEW
23. Which element is a good conductor of
electricity and a solid at standard temperature
and pressure?
A) Nickel
B) Iodine
C) Mercury
D) Sulfur


Correct Answer: Option A - Nickel
Nickel is silvery-white, malleable and ductile metal.
It is one of the elements of the iron group and it takes
on a high polish. It is a solid and a fairly good
conductor of heat and electricity at STP; due to its
characteristic of being bivalent.
REGENTS REVIEW
24. How do the energy and the most probable location
of an electron in the third shell of an atom compare
to the energy and the most probable location of an
electron in the first shell of the same atom?
A) In the third shell, an electron has more energy and is
closer to the nucleus.
B) In the third shell, an electron has less energy and is
closer to the nucleus.
C) In the third shell, an electron has less energy and is
farther from the nucleus.
D) In the third shell, an electron has more energy and is
farther from the nucleus.

Correct Answer: Option D - In the third shell, an
electron has more energy and is farther from the
nucleus.
REGENTS REVIEW
25. A sample composed only of atoms having the
same atomic number is classified as
A) A compound
B) An element
C) A solution
D) An isomer


Correct Answer: Option B - An element
A chemical element is a pure chemical substance
consisting of one type of atom distinguished by its
atomic number, which is the number of protons in its
nucleus. The term is also used to refer to a pure
chemical substance composed of atoms with the same
number of protons.
REGENTS REVIEW
26. What does the wave-mechanical model of
the atom state?
A) Atoms travel in defined circles
B) Atoms are most likely found in an excited
state
C) Atoms have a positive charge
D) Atoms are located in orbitals outside the
nucleus

Correct Answer: Option D - Atoms are
located in orbitals outside the nucleus
REGENTS REVIEW
27. Which two particles each have a mass
approximately equal to one atomic mass
unit?
A) Electron and neutron
B) Electron and positron
C) Proton and neutron
D) Proton and electron

Correct Answer: Option C - Proton and
neutron
REGENTS REVIEW
28. Which phrase describes an atom?
A) A negatively charged electron cloud
surrounding a positively charged nucleus
B) A positively charged electron cloud
surrounding a positively charged nucleus
C) A positively charged electron cloud
surrounding a negatively charged nucleus
D) A negatively charged electron cloud
surrounding a negatively charged nucleus

Correct Answer: Option A - A negatively
charged electron cloud surrounding a
positively charged nucleus
REGENTS REVIEW
29. Among the following combinations, which
total mass is the smallest?
A) The sum of the masses of 1 electron and 1
proton
B) Mass of 2 electrons
C) Mass of 2 neutrons
D) The sum of the masses of 1 neutron and 1
electron

Correct Answer: Option B - Mass of 2
electrons
REGENTS REVIEW
30. Elements on the modern Periodic Table are
arranged in order of increasing
A) Atomic mass
B) Number of neutrons
C) Number of valence electrons
D) Atomic number


Correct Answer: Option D - Atomic number
The atomic number (also known as the proton number) is
the number of protons found in the nucleus of an atom and
therefore identical to the charge number of the nucleus. It
is conventionally represented by the symbol Z. The atomic
number uniquely identifies a chemical element. In an atom
of neutral charge, atomic number is equal to the number of
electrons.