SAT Reading Practice Test-3

This passage is adapted from an article on the history and development of the periodic table.

The periodic table is one of the most recognizable symbols of chemistry, organizing elements according to their atomic number, electron configurations, and recurring chemical properties. The modern periodic table was formulated by Dmitri Mendeleev in 1869, who arranged the elements in a table based on atomic weights and predicted the properties of elements yet to be discovered.

Mendeleev’s table was groundbreaking because it revealed that the properties of elements repeat in a periodic fashion when arranged by increasing atomic weight. This periodicity allowed Mendeleev to leave gaps in his table for elements that had not yet been discovered, and to predict their properties with remarkable accuracy. For example, he predicted the existence and properties of germanium, gallium, and scandium, which were discovered later and found to closely match his predictions.

The periodic table has evolved significantly since Mendeleev’s time. The discovery of the proton and the concept of atomic number led to the modern arrangement of elements by increasing atomic number rather than atomic weight. This corrected anomalies in Mendeleev’s table, such as the placement of argon before potassium despite having a higher atomic weight.

In the 20th century, Glenn T. Seaborg made significant contributions by identifying transuranium elements (elements beyond uranium in the periodic table) and reorganizing the table to include the actinide series. This further refined the structure of the periodic table, providing a more comprehensive framework for understanding chemical behavior.

Today, the periodic table is a fundamental tool in chemistry and other sciences. It not only categorizes all known elements but also provides a predictive framework for discovering new ones. The arrangement of elements reveals the underlying structure of atoms and the relationships between them, enabling scientists to predict chemical reactions and properties of elements with great accuracy.

Questions:

1. The primary purpose of the passage is to:

A. explain the chemical reactions involving elements.B. describe the history and development of the periodic table.C. discuss the applications of the periodic table in modern science.D. outline the properties of newly discovered elements.

2. According to the passage, what was one of Mendeleev’s significant contributions to chemistry?

A. He discovered the proton.B. He arranged elements by increasing atomic number.C. He predicted the existence and properties of undiscovered elements.D. He identified transuranium elements.

3. In the context of the passage, what does the term “periodicity” most nearly mean?

A. Randomness B. Recurrence C. Unpredictability D. Stability

Answers & Explanations

The primary purpose of the passage is to:B. describe the history and development of the periodic table.Explanation: The passage discusses the historical development of the periodic table, starting with Mendeleev’s arrangement based on atomic weight and moving to the modern table organized by atomic number. It also mentions the contributions of other scientists, like Seaborg, to the periodic table’s evolution.

According to the passage, what was one of Mendeleev’s significant contributions to chemistry?C. He predicted the existence and properties of undiscovered elements.Explanation: The passage states that Mendeleev predicted the existence and properties of elements that had not yet been discovered, such as germanium, gallium, and scandium, and that his predictions were remarkably accurate.

In the context of the passage, what does the term “periodicity” most nearly mean?

B. Recurrence

Explanation: The term “periodicity” in the passage refers to the recurring pattern of chemical properties that Mendeleev observed when elements were arranged by increasing atomic weight. This periodicity is a fundamental concept that underlies the organization of the periodic table.

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