Question 1

Which of the following statements best describes the modern atomic theory as it relates to chemical reactions?

Accepted Answer

Chemical reactions change only the way atoms are combined in compounds.

Question 2

A neutral atom of sulfur has an atomic number of 16 and a mass number of 32. How many protons, neutrons, and electrons does it contain?

Accepted Answer

16 protons, 16 neutrons, 16 electrons

Question 3

Which of the following best explains why alkali metals (Group 1A) are never found in nature in their pure state?

Accepted Answer

They are highly reactive and readily combine with other elements.

Question 4

Which isotope notation correctly represents an atom with 17 protons, 18 neutrons, and 17 electrons?

Accepted Answer

$$^{35}_{17}\mathrm{Cl}$$

Question 5

Gallium has two naturally occurring isotopes: $$^{69}\mathrm{Ga} (60.4$$%, mass = 68.9257 amu) and $$^{71}\mathrm{Ga} (39.6$$%, mass = 70.9248 amu). What is the atomic weight of gallium?

Accepted Answer

$$69.7\ \mathrm{amu}$$

Question 6

Which of the following elements is a metalloid?

Accepted Answer

Silicon (Si)

Question 7

Which group on the periodic table contains elements that are colorless, odorless, and extremely unreactive under normal conditions?

Accepted Answer

Group 8A (Noble gases)

Question 8

Which of the following electron configurations represents a neutral magnesium atom?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$

Question 9

Which of the following best describes the trend in atomic radius as you move down a group in the periodic table?

Accepted Answer

Atomic radius increases due to the addition of electron shells.

Question 10

What is the general valence-shell electron configuration for elements in Group 6A?

Accepted Answer

$$ns^2np^4$

Question 11

A tin atom has an atomic number of 50. How many valence electrons does it have, and what is its valence-shell configuration?

Accepted Answer

4 valence electrons; $$5s^2$$ $$5p^2$$

Question 12

Which of the following is the correct electron-dot (Lewis) symbol for a phosphorus atom?

Accepted Answer

P with five dots around it

Question 13

Which of the following statements about electron shells and subshells is correct?

Accepted Answer

The third shell can hold up to 18 electrons, distributed among s, p, and d subshells.

Question 14

Which of the following best explains why electrons fill the 4s orbital before the 3d orbital?

Accepted Answer

The 4s orbital is lower in energy than the 3d orbital.

Question 15

Which of the following elements has the electron configuration $$[Ne]\ 3s^2$\ 3p^5$?

Accepted Answer

Chlorine (Cl)

Question 16

A certain element has the following electron configuration: $$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$\ $$4s^2$$\ $$3d^{10}$$\ $$4p^2. $$What is the element?

Accepted Answer

Germanium (Ge)

Question 17

Which of the following best describes the difference between isotopes of the same element?

Accepted Answer

They have the same number of protons but different numbers of neutrons.

Question 18

Which of the following is a property of halogens (Group 7A)?

Accepted Answer

They are colorful and corrosive nonmetals.

Question 19

Which of the following best describes the arrangement of electrons in an atom according to the quantum mechanical model?

Accepted Answer

Electrons are restricted to certain energy values and are found in orbitals defined by wave functions.

Question 20

Which of the following is the correct shorthand electron configuration for zirconium (Zr)?

Accepted Answer

$$[Kr]\ 5s^2$\ 4d^2$

Atoms and the Periodic Table: Structure, Properties, and Electron Configurations

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