Moseley’s experiments on X rays emitted from atoms led to the concept of atomic numbers. (a) If arranged in order of increasing atomic mass, which element would come after chlorine? (b) Describe two ways in which the properties of this element differ from the other elements in group 8A.

Verified step by step guidance

Step 1: Identify the atomic number of chlorine, which is 17, and its atomic mass, which is approximately 35.5 amu.

Step 2: List the elements in order of increasing atomic mass around chlorine. Chlorine is followed by argon (atomic mass ~39.9 amu) and then potassium (atomic mass ~39.1 amu).

Step 3: Determine which element comes after chlorine when arranged by increasing atomic mass. Argon comes after chlorine in terms of atomic mass.

Step 4: Recognize that argon is a noble gas and belongs to group 8A of the periodic table.

Step 5: Compare argon with other elements in group 8A, noting that argon is a gas at room temperature and is chemically inert, similar to other noble gases, but differs in atomic size and ionization energy.

Key Concepts

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

Atomic Number

The atomic number is the number of protons in the nucleus of an atom, which determines the element's identity and its position in the periodic table. Moseley's work established that elements should be arranged by atomic number rather than atomic mass, leading to a more accurate representation of elemental properties and periodic trends.

Periodic Table Trends

The periodic table is organized in such a way that elements exhibit trends in properties such as electronegativity, ionization energy, and atomic radius. Understanding these trends helps predict how elements will behave chemically and physically, particularly when comparing elements in the same group, like the noble gases in group 8A.

Group 8A (Noble Gases)

Group 8A, also known as the noble gases, includes elements like helium, neon, argon, krypton, xenon, and radon. These elements are characterized by their full valence electron shells, making them largely inert and unreactive compared to other elements. Understanding their unique properties, such as low reactivity and high stability, is essential when comparing them to other elements.

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Textbook Question

Shown below is a qualitative diagram of the atomic orbital energies for an Na atom. The number of orbitals in each subshell is not shown.

(d) A sodium vapor lamp (Figure 7.23) operates by using electricity to excite the highest-energy electron to the next highest-energy level. Light is produced when the excited electron drops back to the lower level. Which two energy levels are involved in this process for the Na atom?

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Textbook Question

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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Textbook Question

Among the elements N, O, P, and S, which element or elementshave the smallest effect nuclear charge if we use Equation7.1 to calculate Zeff? Which element or elements havethe 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. (a) What value do you estimate for Zeff experienced by the outermost electron in both Na and K by assuming core electrons contribute 1.00 and valence electrons contribute 0.00 to the screening constant?