Quiz: Fundamentals of Atomic Structure — 9 domande

1. How do the atomic number and the charge on the nucleus compare?

A. They are always equal and both positive

B. They are unrelated concepts

C. They are always equal but the charge can be negative

D. Atomic number is always greater than the charge

Answer: (A)

Spiegazione

The source states that the charge on the nucleus is always positive and is numerically equal to the atomic number, indicating that they are always equal and both positive, making option 0 correct.

2. How can you determine the net electric charge of an atom that has gained or lost electrons in practice?

A. Subtract the number of protons from the number of electrons to find the charge.

B. Subtract the number of electrons from the number of protons to find the charge.

C. Multiply the number of protons by the number of electrons to find the charge.

D. Add the number of protons and electrons to find the charge.

Answer: (B)

Spiegazione

The net electric charge is determined by subtracting the number of electrons from the number of protons. Gaining electrons results in a negative charge, while losing electrons results in a positive charge. The source explicitly states that the charge equals the number of protons minus the number of electrons, making option 1 the correct method.

3. What does the term 'ion' specifically refer to in atomic and molecular terms?

A. A neutral atom with equal protons and electrons

B. A molecule with a full outer electron shell

C. A charged particle formed by gaining or losing electrons

D. An atom with a fixed number of neutrons

Answer: (C)

Spiegazione

The source explicitly states that an ion is an atom or molecule that has gained or lost electrons, resulting in a charged particle. This distinguishes ions from neutral atoms and molecules with balanced charges. The other options describe different concepts: a neutral atom (option 0), a stable molecule (option 2), and an atom's neutrons (option 3), which are unrelated to the definition of an ion.

4. What is a direct consequence of an increase in the number of neutrons in an atom's nucleus?

A. The atomic number decreases, reverting the element to a previous state.

B. The atomic mass increases, affecting the isotope's mass.

C. The number of electrons decreases, altering the charge.

D. The atomic number increases, changing the element.

Answer: (B)

Spiegazione

An increase in the number of neutrons adds to the total count of protons and neutrons in the nucleus, thereby increasing the atomic mass. Since atomic mass equals protons plus neutrons, more neutrons lead to a higher atomic mass, affecting the isotope's mass. The atomic number, which equals protons, remains unchanged by neutrons, and electrons are not directly affected by neutron count.

5. Who formulated the principle that electrons fill atomic orbitals starting from the lowest energy level?

A. Niels Bohr

B. Dmitri Mendeleev

C. Gilbert Lewis

D. Erwin Schrödinger

Answer: (D)

Spiegazione

The Aufbau principle, which describes how electrons fill orbitals starting from the lowest energy level, was formulated by Gilbert Lewis. The source explicitly attributes this principle to an author, and among the options, Gilbert Lewis is the correct attribution.

6. What does the term 'shell' refer to in atomic structure?

A. A region where electrons are most likely to be found

B. A specific energy level occupied by a single electron

C. A region of space where electrons are forbidden from entering

D. A set of orbitals with the same principal quantum number (n)

Answer: (D)

Spiegazione

A shell in atomic structure refers to a set of orbitals with the same principal quantum number (n), indicating a group of energy levels at a similar energy range around the nucleus. This concept helps organize the electron configuration within an atom.

7. Arrange the following principles related to electron configurations in the order they were established historically.

A. Hund's rule, Aufbau principle, Pauli exclusion principle

B. Aufbau principle, Pauli exclusion principle, Hund's rule

C. Pauli exclusion principle, Aufbau principle, Hund's rule

D. Aufbau principle, Hund's rule, Pauli exclusion principle

Answer: (C)

Spiegazione

The Aufbau principle was formulated before the Pauli exclusion principle, and Hund's rule was established after both. The correct chronological order is Aufbau, Pauli, then Hund.

8. What is the primary function of valence electrons in an atom?

A. They contribute to the atom's mass.

B. They are involved in chemical bonding and reactions.

C. They determine the atom's atomic number.

D. They are responsible for the atom's stability.

Answer: (B)

Spiegazione

Valence electrons are electrons in the outermost shell of an atom. Their primary function is to participate in chemical bonding and reactions, as they determine how atoms interact chemically. The other options are incorrect: atomic number is determined by protons, not valence electrons; mass is mainly due to protons and neutrons; stability is related to the full outer shell, but the core function of valence electrons is their role in bonding.

9. What is the primary basis for the organization of elements in the periodic table?

A. Electronegativity of the elements

B. Atomic number of the elements

C. Number of valence electrons

D. Atomic mass of the elements

Answer: (B)

Spiegazione

The periodic table is organized primarily by increasing atomic number, which determines the element's position in the table. This arrangement reflects periodic trends and groups of elements with similar properties based on their valence electrons, but the fundamental organizing principle is the atomic number.