Can you give me a Biography about Mendeleev's Periodic Table?

In which of the following belong to a category called the main group of elements? nonmetals. transition elements. halogens. alkali metals. it can be more than one answer!

The blackbody curve for a star name zeta is shown below. what is the peak wavelength for this star ?

Ageochemist examines a piece of metal that he found in the soil. he performs tests to identify the metal from its density, electrical conductivity, and melting point. which statement best describes his investigation? a. he is determining physical properties that are sufficient to identify the metal. b. he is determining chemical properties that are sufficient to identify the metal. c. he is determining physical properties that are insufficient to identify the metal. d. he is determining chemical properties that are insufficient to identify the metal.