Question

Which of the following is not correct statement for periodic classification of elements? (a) The properties of elements are the periodic functions of their atomic number. (b) Non-metallic elements are less in number than metallic elements. (c) For transition elements, the last electron enters into \((n-2) d\)-subshell. (d) None of these

Short answer

The incorrect statement for the periodic classification of elements is (d) None of these.

Step-by-step solution

Analyzing Statement A

Statement A states that 'The properties of elements are the periodic functions of their atomic number.' This is a correct statement because in the modern periodic table, elements are arranged in order of increasing atomic number, and properties do recur periodically.

Analyzing Statement B

Statement B states that 'Non-metallic elements are less in number than metallic elements.' This is also correct. In the periodic table, there are more metals than non-metals.

Analyzing Statement C

Statement C states that 'For transition elements, the last electron enters into \(n-2) d\)-subshell.' This is correct for transition elements. They are defined by the fact that the last electron added occupies a d-sublevel.

Identifying Incorrect Statement

Since all the given statements A, B, and C are correct, the incorrect statement must be (d) 'None of these.'

Key concepts

Modern Periodic Table

The modern periodic table is a vital tool for chemists, physicists, and anyone interested in the study of elements. It is arranged based on the atomic number, which is the number of protons found in the nucleus of an atom of an element. Unlike earlier versions, such as Mendeleev's periodic table which was based on atomic mass, the modern version offers a more accurate reflection of the elements' properties.

Elements are arranged in rows called periods and columns known as groups, with elements in the same group having similar chemical properties. A remarkable feature of the modern periodic table is the periodic law, which states that the properties of elements are periodic functions of their atomic numbers.

The table also identifies four blocks – s, p, d, and f – based on the subshell in which the final electron resides. Knowing how the table is organized helps students predict the properties of elements, such as their valency, metallic character, and reactivity, enhancing their comprehension of chemical behavior.

Atomic Number

In chemistry, the atomic number is a fundamental property of an element, as it defines the element's unique identity. It is denoted by the letter 'Z' and reflects the number of protons present in one atom's nucleus, which also equals the number of electrons in a neutral atom. The atomic number is pivotal because it determines the chemical behavior of the element: it allows the elements to be organized in the periodic table and dictates their placement.

Periodicity, which is the repetition of properties at regular intervals, arises due to the pattern of electron configuration that changes systematically with the atomic number. This makes the atomic number crucial for predicting how an element will react chemically. For instance, elements with similar outer electron arrangements exhibit similar properties, grouping them into families such as the noble gases or halogens.

Transition Elements

Transition elements are metals located in the central block of the periodic table, specifically in the d-block, and include groups 3 through 12. What characterizes these elements is the gradual filling of their d-orbitals with electrons. As per the statement '(c)', for transition elements, the last electron enters the \(n-2)d\)-subshell.

These elements display a wide range of oxidation states and form various colored compounds, making them easily distinguishable. They often have high melting points, are good conductors of heat and electricity, and possess magnetic properties. Transition metals play a pivotal role in many biological processes and are also widely used in industry for their catalytic and structural abilities.

Understanding the nuances of transition elements, such as the concept of variable valency and their tendency to form coordination compounds, is crucial for students studying chemistry, as it helps explain a plethora of chemical reactions and interactions.