Modern Periodic Table

Anomalies in arrangement of elements based on increasing atomic mass could be removed when the elements were arranged in order of increasing atomic number, a fundamental property of the element discovered by Henry Moseley. Henry Moseley gave the modern periodic law, which states that, the physical and chemical properties of elements are a periodic function of their atomic numbers. If the elements are arranged in the order of their increasing atomic numbers, the elements with similar properties are repeated at regular intervals. Elements in the Modern Periodic Table are arranged in 18 vertical columns called groups and 7 horizontal rows called periods. The recurrence of same properties after a fixed interval when the elements are arranged in increasing order of their atomic numbers is known as periodicity. The properties of elements that reappear at regular intervals or that show gradual variation at regular intervals in the modern periodic table are called periodic properties. Elements thus arranged show periodicity of properties including atomic size, valency or combining capacity and metallic and non-metallic character.

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  • Q1

    Identify the correct statement from the following

    Marks:1
    Answer:

    Group 18 elements are called noble gases.

    Explanation:

    The outermost orbit of group 18 elements is completely filled. Due to stable electronic configuration, they have no tendency to react with other elements. Hence, these elements are called inert or noble gases.

    Group 2 elements are called alkaline earth metals.

    Group 17 elements are called halogens.

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  • Q2

    The first member of group 13 of the modern periodic table is

    Marks:1
    Answer:

    boron.

    Explanation:

    Group 13 of the modern periodic table is also known as Boron family. Boron (B) is the first member of this group.

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  • Q3

    With reference to modern periodic table, Chalcogens is another name of

    Marks:1
    Answer:

    group 16.

    Explanation:

    Group 16 of the modern periodic table is known as oxygen family. The elements of this group are also called chalcogens that means ore forming.

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  • Q4

    The number of electron shells present in the elements of third period of the modern periodic table is/are

    Marks:1
    Answer:

    3

    Explanation:

    All the elements belonging to third period of modern periodic table have 3 shells/orbits. Number of shells remains constant on moving from left to right.

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  • Q5

    The modern periodic law was given by

    Marks:1
    Answer:

    Henry Moseley.

    Explanation:

    The modern periodic law was given by Henry Moseley. According to this law, ‘Physical and chemical properties of elements are periodic functions of their atomic numbers’. The modern periodic table is based on this law.

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