Question

Which of the following statement is false? (1) In modern periodic table the elements are arranged in increasing order of atomic number. (2) The number of periods in the long form periodic table is \(7 .\) (3) The long form periodic table is nothing but just a graphical representation of Paulis principle. (4) Elements of III period are called typical elements.

Short answer

Statement (3) is false. The long form periodic table is not just a graphical representation of Pauli's principle.

Step-by-step solution

Understand the Statements

First, understand each statement given:Statement (1): In the modern periodic table, the elements are arranged in increasing order of atomic number.Statement (2): The number of periods in the long form periodic table is 7.Statement (3): The long form periodic table is nothing but just a graphical representation of Pauli's principle.Statement (4): Elements of III period are called typical elements.

Verify Statement 1

Check if statement (1) is true or false:The modern periodic table does arrange elements in increasing order of atomic number. This statement is true.

Verify Statement 2

Check if statement (2) is true or false:There are indeed 7 periods in the long form periodic table. This statement is true.

Verify Statement 3

Check if statement (3) is true or false:The long form periodic table is not just a graphical representation of Pauli's principle. Pauli's exclusion principle states that no two electrons in an atom can have the same set of quantum numbers. The periodic table is based on electron configurations and periodic law. This statement is false.

Verify Statement 4

Check if statement (4) is true or false:Elements of the III period (third period) are indeed often referred to as typical elements. This statement is true.

Key concepts

Atomic Number

The atomic number of an element is the number of protons found in the nucleus of an atom. This number is unique to each element and is what differentiates one element from another.

In the modern periodic table, elements are arranged in order of increasing atomic number. This arrangement reflects the periodic recurrence of chemical properties.

For example, hydrogen, with an atomic number of 1, is placed first, followed by helium with an atomic number of 2, lithium with 3, and so on. The atomic number not only determines the position of the element in the periodic table, but it also gives valuable information about the element’s electronic configuration.

This systematic arrangement helps predict the chemical behavior of elements.

Periods in Periodic Table

The periodic table is divided into horizontal rows called periods. Each period represents a principal energy level that is being filled with electrons. There are seven periods in the modern periodic table:

• 1st Period: Contains only 2 elements, hydrogen and helium.
• 2nd Period: Contains 8 elements, from lithium to neon.
• 3rd Period: Contains 8 elements, from sodium to argon.
• 4th Period: Contains 18 elements, from potassium to krypton.
• 5th Period: Contains 18 elements, from rubidium to xenon.
• 6th Period: Contains 32 elements, from cesium to radon, including lanthanides.
• 7th Period: Contains 32 elements, from francium onwards, including actinides.

The length of each period depends on the number of electrons that can occupy the sublevels being filled in that period.

Understanding the structure of periods can help in predicting the properties and behaviors of elements.

Pauli Exclusion Principle

The Pauli Exclusion Principle is a fundamental tenet of quantum mechanics. It states that no two electrons in the same atom can have the same set of four quantum numbers (maximal set of quantum numbers).

This principle explains the arrangement of electrons within atoms. Each electron in an atom has a unique set of quantum numbers describing its energy, angular momentum, magnetic moment, and spin.

• Principal Quantum Number (n): Indicates the energy level of the electron.
• Angular Momentum Quantum Number (l): Relates to the shape of the orbital.
• Magnetic Quantum Number (m_l): Represents the orientation of the orbital.
• Spin Quantum Number (m_s): Describes the spin direction of the electron.

The periodic table uses the arrangement of electrons to categorize and predict the properties of elements, but it is not simply a graphical representation of the Pauli Exclusion Principle. It is based on electron configurations and the periodic law.

Typical Elements

Typical elements refer to the elements found in the third period of the periodic table. They include:

• Sodium (Na)
• Magnesium (Mg)
• Aluminum (Al)
• Silicon (Si)
• Phosphorus (P)
• Sulfur (S)
• Chlorine (Cl)
• Argon (Ar)

These elements are called typical because their properties are well-understood and they exhibit a transition from metals to nonmetals.

For example:

• Metals: Sodium and magnesium are metallic, with typical metallic properties like good conductivity and malleability.
• Metalloids: Silicon has properties intermediate between metals and nonmetals and is crucial in the electronics industry.
• Nonmetals: Sulfur and chlorine show nonmetallic properties, like poor conductivity and brittleness.

Understanding the typical elements helps in grasping trends across periods and predicting the behavior of elements in their group.