Cortège électronique et tableau périodique Practice Quiz (9 questions)

1. Which description identifies an atom’s outermost electron shell?

A. The last shell containing at least one electron, which may include several subshells

B. The shell with the greatest number of electrons, which cannot include subshells

C. The first shell filled during electron placement, which contains core electrons

D. The shell containing the atom’s most energetic electrons, which has one subshell

Answer: (A)

Explanation

The outermost shell is the last shell that contains at least one electron, and it can have multiple subshells. The shell filled first is an inner shell, not the outermost one.

2. What distinguishes valence electrons from core electrons in an atom?

A. Valence electrons are found in every shell and cannot participate in chemical bonding

B. Valence electrons occupy the outer shell and can participate in chemical bonding

C. Valence electrons occupy the outer shell but do not contribute to chemical bonding

D. Valence electrons occupy inner shells and primarily determine the atom’s mass

Answer: (B)

Explanation

Valence electrons are in the outer shell and can participate in forming chemical bonds. Electrons in inner shells are core electrons, rather than valence electrons.

3. What is the maximum number of electrons in a shell with principal quantum number $n=3$?

A. 9 electrons

B. 6 electrons

C. 18 electrons

D. 32 electrons

Answer: (C)

Explanation

A shell with principal quantum number $n$ holds at most $2n^2$ electrons, giving $2(3)^2=18$ for this shell. The value 9 comes from using $n^2$ rather than the stated maximum-capacity rule.

4. An atom has a subshell with capacity for six electrons; which type of subshell is it?

A. An s subshell

B. A shell with principal quantum number 3

C. A p subshell

D. A shell with principal quantum number 2

Answer: (C)

Explanation

A p subshell can hold up to six electrons, whereas an s subshell holds up to two. The shell labels do not by themselves specify the capacity of a particular subshell.

5. What does an atom’s electron configuration describe?

A. How its occupied shells are arranged in the periodic table

B. How its electrons are distributed among its subshells

C. How its chemical bonds are distributed around its outer shell

D. How its protons are distributed among its nuclear energy levels

Answer: (B)

Explanation

An electron configuration specifies the distribution of an atom’s electrons among its subshells. The periodic table can help infer that distribution, but it is not itself the arrangement being described.

6. In what year did Dimitri Mendeleïev establish the basis of the modern periodic classification?

A. 1879

B. 1869

C. 1859

D. 1896

Answer: (B)

Explanation

Mendeleïev established the basis of the modern periodic classification in 1869. The year 1859 predates this milestone by a decade.

7. What is the role of an element’s position in the periodic table when studying its electron arrangement?

A. It can be used to infer the element’s electron configuration.

B. It specifies the order in which the element forms chemical bonds.

C. It determines the maximum capacity of each occupied subshell.

D. It identifies the number of neutrons in the element’s nucleus.

Answer: (A)

Explanation

An element’s position in the periodic table can help infer its electron configuration, and the relationship also works in reverse. The neutron count is not determined by an element’s table position, since isotopes of the same element can have different neutron numbers.

8. At what stage of an atom’s electron arrangement are its valence electrons found?

A. In the shell immediately below the outermost occupied shell, where they form the core

B. In the outermost occupied shell, where they may participate in chemical bonding

C. In the innermost occupied shell, where they determine the atomic number

D. In any subshell that has room for additional electrons

Answer: (B)

Explanation

Valence electrons occupy the outermost shell containing electrons and can participate in forming chemical bonds. Electrons in inner shells are core electrons, not valence electrons.

9. How do the maximum electron capacities of an s subshell and a p subshell compare?

A. Both subshell types hold up to 6 electrons.

B. An s subshell holds up to 6 electrons, while a p subshell holds up to 2.

C. Both subshell types hold up to 2 electrons.

D. An s subshell holds up to 2 electrons, while a p subshell holds up to 6.

Answer: (D)

Explanation

An s subshell can contain at most 2 electrons, whereas a p subshell can contain up to 6. The reverse comparison is incorrect because it assigns each subshell the other type’s capacity.