ATOMIC CONCEPTSRegents Review

REGENTS REVIEW1. A neutron has approximately the same

mass as a

A)    An alpha particleB)    A beta particleC)    An electronD)    A proton

Correct Answer: Option D - A proton

REGENTS REVIEW2. Which atom contains exactly 15 protons?

A)    P-32B)    S-32C)    O-15D)    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 REVIEW3. When electrons in an atom in an excited

state fall to lower energy levels, energy isA)    Absorbed, onlyB)    Released, onlyC)    Neither released nor absorbedD)    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 REVIEW4. What is the mass number of an atom which contains 28

protons, 28 electrons, and 34 neutrons? A)    28B)    62C)    56D)    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 REVIEW5. Atoms of the same element that have different

numbers of neutrons are classified as:A)    IsotopesB)    Charged atomsC)    IsomersD)    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 REVIEW6. Which symbols represent atoms that are

isotopes? A)    C-14 and N-14B)    O-16 and O-18C)    Rn-222 and Ra-222D)    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 REVIEW7. Compared to the charge and mass of a proton, an

electron has A)    The same charge and a smaller massB)    The same charge and the same massC)    An opposite charge and a smaller massD)    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 REVIEW8. 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 massB)    More massC)    Less energyD)    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 REVIEW9. What is the atomic number, of an ion with 5 protons, 6

neutrons, and a charge of 3+? A)    5B)    6C)    8D)    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 REVIEW10. In which group do the particles

contain only nucleons?

A)    Protons and electronsB)    Neutrons and electronsC)    Protons and neutronsD)    Protons, neutrons, and electrons

Correct Answer: Option C - Protons and neutrons

REGENTS REVIEW11. What is the electron configuration of

a sulfur atom in the ground state?

A)    2-4B)    2-8-4C)    2-6D)    2-8-6

Correct Answer: Option D - 2-8-6

REGENTS REVIEW12. Which element's ionic radius is smaller than

its atomic radius? A)    NeonB)    SodiumC)    NitrogenD)    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 REVIEW13. What is the total number of neutrons in an atom of 

5726Fe?

A)    26B)    57C)    31D)    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 REVIEW14. In which shell are the valence electrons of the elements

in Period 2 found? A)    1B)    2C)    3D)    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 REVIEW15. How many electrons are in the

outermost principal energy level of an atom of carbon in the ground state?

A)    6B)    2C)    3D)    4

Correct Answer: Option D - 4 The electronic configuration of carbon in the

ground state is:

REGENTS REVIEW16. 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)    DeuteronsB)    NeutronsC)    ProtonsD)    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 REVIEW17. The elements in Period 3 all contain

the same number of

A)    Occupied principal energy levelsB)    ProtonsC)    NeutronsD)    Valence electrons

Correct Answer: Option A - Occupied principal energy levels

REGENTS REVIEW18. 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 REVIEW19. What is the atomic number of an element that has

six protons and eight neutrons? A)    8B)    10C)    6D)    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 REVIEW21. An atom is electrically neutral becauseA)    Number of protons equals the number of

electronsB)    Number of protons equals the number of

neutronsC)    Ratio of the number of neutrons to the

number of electrons is 1:1D)    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 REVIEW22. Atoms of which element have the

greatest tendency to gain electrons?

A)    BromineB)    FluorineC)    ChlorineD)    Iodine

Correct Answer: Option B - Fluorine

REGENTS REVIEW23. Which element is a good conductor of

electricity and a solid at standard temperature and pressure?

A)    NickelB)    IodineC)    MercuryD)    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 REVIEW24. 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 REVIEW25. A sample composed only of atoms having the

same atomic number is classified as A)    A compoundB)    An elementC)    A solutionD)    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 REVIEW26. What does the wave-mechanical

model of the atom state? A)    Atoms travel in defined circlesB)    Atoms are most likely found in an excited

stateC)    Atoms have a positive chargeD)    Atoms are located in orbitals outside the

nucleus

Correct Answer: Option D - Atoms are located in orbitals outside the nucleus

REGENTS REVIEW27. Which two particles each have a mass

approximately equal to one atomic mass unit?

A)    Electron and neutronB)    Electron and positronC)    Proton and neutronD)    Proton and electron

Correct Answer: Option C - Proton and neutron

REGENTS REVIEW28. Which phrase describes an atom? A)    A negatively charged electron cloud

surrounding a positively charged nucleusB)    A positively charged electron cloud

surrounding a positively charged nucleusC)    A positively charged electron cloud

surrounding a negatively charged nucleusD)    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 REVIEW29. Among the following combinations,

which total mass is the smallest? A)    The sum of the masses of 1 electron and 1

protonB)    Mass of 2 electronsC)    Mass of 2 neutronsD)    The sum of the masses of 1 neutron and 1

electron

Correct Answer: Option B - Mass of 2 electrons

REGENTS REVIEW30. Elements on the modern Periodic Table are arranged

in order of increasing A)    Atomic massB)    Number of neutronsC)    Number of valence electronsD)    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.