Question

The statement that is not correct for periodic classification of elements is: (a) The properties of elements are a periodic function of their atomic numbers (b) Non-metallic elements are less in number than metallic elements (c) The first ionization energies of elements along a period do not vary in a regular manner with in crease in atomic number (d) For transition elements, the d-subshells are filled with electrons monotonically with increase in atomic number

Short answer

Statement (d) is not correct.

Step-by-step solution

Analyze Statement (a)

Statement (a) is correct. The periodic law states that the properties of elements are a periodic function of their atomic numbers. This is the basis of the modern periodic table.

Analyze Statement (b)

Statement (b) is correct. There are fewer non-metallic elements compared to metallic elements in the periodic table.

Analyze Statement (c)

Statement (c) is correct. The first ionization energy generally increases across a period but does not strictly vary in a regular manner due to some irregularities caused by electron configurations.

Analyze Statement (d)

Statement (d) is incorrect. For transition elements, the d-subshells are not always filled in a straightforward, monotonic manner with increasing atomic number due to the relative energies of s and d orbitals which may lead to exceptions.

Key concepts

Periodic Law

The periodic law is a key principle in chemistry that helps us understand how elements are organized and classified. It states that the properties of elements are a periodic function of their atomic numbers. This means that when elements are arranged in order of increasing atomic number, certain properties appear at regular intervals or periods.
This concept is fundamental to the construction of the modern periodic table, where elements with similar properties are grouped together in columns, called groups or families. The periodic law allows chemists to predict the properties of elements based on their position in the table, providing a powerful tool for studying and applying chemistry.

Ionization Energy

Ionization energy is the amount of energy required to remove an electron from an atom or ion. As you move across a period in the periodic table from left to right, ionization energy generally increases. This is because the atomic radius decreases, and the outer electrons are closer to the nucleus and more strongly attracted to it.
However, this increase is not always perfectly regular. There are exceptions due to the specific electron configurations of certain elements. For instance, elements with half-filled or fully filled subshells are more stable, and thus may have higher ionization energies than expected.

• It is important to understand that these variations are common and reflect the complex nature of electron interactions within atoms.

Transition Elements

Transition elements are unique because they include elements where the d-subshell is being filled with electrons. These elements are found in the d-block of the periodic table and display unique properties such as the formation of colored compounds, variability in oxidation states, and the ability to form complex ions.
An interesting aspect of transition elements is that their d-subshells are not filled in a simple, systematic order. The relative energies of the 3d, 4s, and other orbitals can lead to exceptions in the electron configurations, causing significant variety within these elements. This complexity often leads to these elements exhibiting similar chemical behaviors despite differences in atomic number.

Modern Periodic Table

The modern periodic table is organized based on the periodic law, arranging elements by increasing atomic numbers. It presents a comprehensive structure for understanding elemental properties and relationships. Each element is placed in a specific group and period that determines its chemical behavior.
The table provides a visual guide to properties such as ionization energy, electron affinity, atomic radius, and metallic character. Understanding the layout and principles behind the periodic table is essential for exploring and predicting the chemical behavior of elements. Elements in the same group tend to have similar properties due to the same number of valence electrons, showcasing the power of organized scientific knowledge.