Ch.7 - Periodic Properties of the Elements

Problem 10

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Chapter 7, Problem 10

The prefix eka- comes from the Sanskrit word for 'one.' Mendeleev used this prefix to indicate that the unknown element was one place away from the known element that followed the prefix. For example, eka-silicon, which we now call germanium, is one element below silicon. Mendeleev also predicted the existence of eka-manganese, which was not experimentally confirmed until 1937 because this element is radioactive and does not occur in nature. Based on the periodic table shown in Figure 7.1, what do we now call the element Mendeleev called eka-manganese?

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Identify the position of manganese on the periodic table. Manganese is element number 25.

Understand the prefix 'eka-' used by Mendeleev, which indicates that the unknown element is one place below the known element in the periodic table.

Locate the element that is directly below manganese in the periodic table. This element will be in the same group but the next period.

Refer to the periodic table to find the atomic number of the element that is directly below manganese.

Identify the element by its atomic number and name, which is what Mendeleev referred to as eka-manganese.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Periodic Table

The periodic table is a systematic arrangement of elements based on their atomic number, electron configuration, and recurring chemical properties. Elements are organized in rows (periods) and columns (groups), which reflect their similarities. Understanding the layout of the periodic table is crucial for identifying relationships between elements, such as those predicted by Mendeleev.

Element Prediction

Element prediction refers to the process of inferring the existence of undiscovered elements based on trends observed in the periodic table. Mendeleev's use of the prefix 'eka-' exemplifies this, as he predicted elements like eka-silicon and eka-manganese by identifying gaps in the table. This concept highlights the predictive power of the periodic table in understanding elemental properties.

Radioactivity

Radioactivity is the process by which unstable atomic nuclei lose energy by emitting radiation. This phenomenon is significant in the context of elements like eka-manganese, which is now known as technetium. Understanding radioactivity is essential for recognizing why certain elements may not be found in nature and how they can be synthesized in laboratories.

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Related Practice

Textbook Question

In the following reaction

which sphere represents a metal and which represents a nonmetal?

The graph below shows the ionization energies for a particular element. In which group is the element most likely a member of? [Section 7.3]

Textbook Question

Group 1A and 2A elements are sometimes called, collectively, “the s-block.” Therefore, what is an analogous name for the entire collection of the group 3A, 4A, 5A, 6A, 7A, and 8A elements?

Textbook Question

Among elements 1–18, which element or elements have the smallest effective nuclear charge if we use Equation 7.1 to calculate 𝑍eff? Which element or elements have the largest effective nuclear charge?

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Textbook Question

Which of the following statements about effective nuclear charge for the outermost valence electron of an atom is incorrect? (i) The effective nuclear charge can be thought of as the true nuclear charge minus a screening constant due to the other electrons in the atom. (ii) Effective nuclear charge increases going left to right across a row of the periodic table. (iii) Valence electrons screen the nuclear charge more effectively than do core electrons. (iv) The effective nuclear charge shows a sudden decrease when we go from the end of one row to the beginning of the next row of the periodic table. (v) The change in effective nuclear charge going down a column of the periodic table is generally less than that going across a row of the periodic table

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Textbook Question

Detailed calculations show that the value of Zeff for the outermost electrons in Na and K atoms is 2.51+ and 3.49+, respectively. (e) Predict Zeff for the outermost electrons in the Rb atom based on the calculations for Na and K.

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