Question

1. choose the best answer.

which scientist created a standard for calculating atomic mass that was later used to form the periodic table?
alexandre - émile béguyer de chancourtois
dimitri mendeleev
julius lothar meyer
stanislao cannizzzaro

1. choose the best answer.

periodicity is the repetition of chemical properties according to _____
electron amount
atomic number
size of nucleus
element name

Explanation:

For question 3: Stanislao Cannizzaro clarified the concept of atomic mass, which was crucial for the development of the periodic table. Dimitri Mendeleev is known for the periodic table itself but not for creating the atomic - mass standard. Alexandre - Emile Béguyer de Chancourtois and Julius Lothar Meyer also made contributions related to periodicity but not the atomic - mass standard.
For question 4: Periodicity in chemical properties is based on the atomic number. The electron amount is related but the modern understanding of periodicity is based on atomic number (number of protons). The size of the nucleus and element name do not determine periodicity.

Answer:

1. Stanislao Cannizzaro
2. atomic number