Consider the following statement : "Atomic number of an element is a more fundamental property than its atomic mass." Who among the following scientists has made the above statement ?

The correct answer is B, Henry Moseley. In 1913 the English physicist Henry Moseley showed that atomic number, not atomic mass, is the fundamental property of an element. He studied the X-rays given off by different elements and found that the square root of their frequency rose steadily with the element's position in the periodic table. This showed that each element has a fixed whole number, its atomic number, equal to the positive charge on its nucleus. On this basis the modern periodic law states that the properties of elements are a periodic function of their atomic numbers. It explained anomalies such as argon coming before potassium despite its greater mass. Moseley was killed in the First World War in 1915. Option A is wrong because Mendeleev arranged his 1869 periodic table by atomic mass. Option C is wrong because J.J. Thomson discovered the electron in 1897 and proposed the plum pudding model. Option D is wrong because Rutherford discovered the atomic nucleus through the gold foil experiment in 1911. Exam tip: Mendeleev ordered elements by atomic mass, Moseley by atomic number, which is the modern periodic law.