Question

During the 1800s, when most of the elements were being

discovered, many chemists tried to classify the elements
based on their:
a Similarities
b Atomic mass
c Atomic numbers
d None of the above

Answer 1

Chemists in the 1800s, including Mendeleev, tried to classify elements mainly based on their atomic mass and similarities in chemical properties; the development of atomic number-based classification by Moseley refined this organization.

Step-by-step explanation:

During the 1800s, when most of the elements were being discovered, many chemists tried to classify the elements based on their atomic mass and similarities in chemical properties. One such chemist, Dmitri Mendeleev, created the periodic table, arranging the elements by increasing atomic mass while also considering their chemical behavior, which he noted repeated at regular intervals—a concept known as 'periodicity.' Mendeleev's organization of elements left gaps for undiscovered elements and even allowed for predictions of their properties. During this time, some elements had to be listed out of order by their atomic mass to align them with others of similar properties. Later on, Henry Moseley's use of X-ray spectroscopy to determine atomic numbers refined the table, solving discrepancies that arose from just using atomic masses.

Answer 2

A; There Similarities