The modern periodic table arranges elements in order of increasing:
A. Atomic mass
B. Mass number
C. Atomic number
D. Number of neutrons
Answer: Option C
Solution (By JKExamLibrary)
The modern periodic law, established by Henry Moseley, states that the properties of elements are periodic functions of their atomic numbers. Mendeleev’s original table was based on atomic mass, but the modern version uses atomic number which resolves anomalies like Ar (Z=18, mass 40) and K (Z=19, mass 39).
Explanation:
Vitamin C is chemically known as ascorbic acid (C6H8O6). It is a vital nutrient involved in the repair of tissue and the enzymatic production of certain neurotransmitters. Deficiency leads to scurvy. Retinol is Vitamin A, Calciferol is Vitamin D, and Tocopherol is Vitamin E.
Assertion (A): Covalent compounds generally have low melting points. Reason (R): The intermolecular forces in covalent compounds are weak compared to ionic compounds.
A.Both A and R are true but R is NOT the correct explanation of A.
B.A is true but R is false.
C.A is false but R is true.
D.Both A and R are true and R is the correct explanation of A.
Explanation:
Covalent compounds consist of molecules held together by weak van der Waals forces, unlike the strong electrostatic forces in ionic lattices. Therefore, less heat energy is required to break these intermolecular forces, resulting in low melting and boiling points. Both statements are true and R correctly explains A.
Explanation:
Atomic number 15 is phosphorus. Electronic configuration: 2, 8, 5. Number of shells = 3 (Period 3). Valence electrons = 5, so it is in group 15 (10+5) for p-block elements. Group 5 is for d-block. Thus Group 15, Period 3.
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