Is the following statement true or false

Is the following statement true or false? The periodic law states that when elements are arranged in order of increasing atomic number, there is a periodic repetition of physical and chemical properties.

The correct answer and explanation is :

Answer: True

The periodic law states that when elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties. This principle forms the foundation of the modern periodic table and explains why elements within the same group (vertical columns) exhibit similar characteristics.

Explanation:

The periodic law was first proposed by Dmitri Mendeleev in 1869, but he initially arranged elements by increasing atomic mass. However, later refinements, particularly by Henry Moseley in 1913, led to the realization that atomic number (the number of protons in an atom’s nucleus) is the key organizing principle, rather than atomic mass.

Periodic Trends and Properties:

1. Groups and Periods: The periodic table is structured in groups (columns) and periods (rows). Elements in the same group have similar valence electron configurations, which determines their chemical behavior.
2. Repetition of Properties: As elements are arranged in order of increasing atomic number, their properties repeat in a predictable manner. For example:

• Alkali metals (Group 1) are highly reactive and form similar compounds.
• Noble gases (Group 18) are chemically inert due to their stable electron configurations.
• Transition metals exhibit gradual changes in properties.

1. Trends in the Periodic Table:

• Atomic radius decreases across a period and increases down a group.
• Ionization energy (energy to remove an electron) increases across a period and decreases down a group.
• Electronegativity (tendency to attract electrons) follows similar trends.

This periodic repetition of properties proves that the arrangement by atomic number is fundamental to understanding chemical behavior, making the periodic law one of the most important principles in chemistry.