Question

1. which statements about the development of the periodic table of elements are true? 1. the modern periodic table is arranged by decreasing atomic number. 2. mendeleevs periodic table had empty spaces which elements that hadnt been discovered yet. 3. the periodic table was never arranged by increasing atomic mass. 4. moseleys periodic table was arranged by increasing atomic number. 5. mendeleev created a periodic table in which the elements by order of valence electrons. a) 1,4 and 5 are true b) 2 and 3 are true c) 2 and 4 are true d) 1 and 2 are true

Explanation:

1. The modern periodic table is arranged by increasing atomic number, not decreasing.
2. Mendeleev's periodic table had empty spaces for elements that hadn't been discovered yet.
3. The periodic table was arranged by increasing atomic mass initially, but this had some issues and was later refined.
4. Moseley's work led to the arrangement of elements by increasing atomic number.
5. Mendeleev created a periodic table where elements were arranged by certain properties including atomic mass - related trends and predicted properties of undiscovered elements.

Answer:

1. False
2. True
3. False
4. True
5. True

So the answer is C (2 and 4 are true)