d and f BLOCK ELEMENTS

Which element trio forms a Dobereiner triad with atomic weights approximately 40, 88, and 137?

• Be, Mg, Ca
• Mg, Ca, Sr
• Ca, Sr, Ba
• Sr, Ba, Ra

Which element trio forms a Dobereiner triad with atomic weights approximately 35.5, 80, and 127?

• N, P, As
• S, Se, Te
• Cl, Br, I
• O, S, Se

Which element trio forms a Dobereiner triad with atomic weights approximately 7, 23, and 39?

• F, Cl, Br
• Li, Na, K
• H, Li, Na
• Be, Mg, Ca

What common principle did Mendeleev and Meyer propose independently in 1869?

• Elements combine in simple whole number ratios
• Atoms are the smallest unit of matter
• Properties of elements recur periodically with increasing atomic weight
• Electrons occupy specific energy levels

Which French geologist created an early periodic arrangement by plotting elements on a cylinder?

• Antoine Lavoisier
• A.E.B. de Chancourtois
• Alexandre Beguyer de Chancourtois
• Georges Urbain