To categorize the elements, what reactions did mendeleev observe?

reactions of elements with helium and lithium

reactions of elements with boron and beryllium

reactions of elements with nitrogen and carbon

reactions of elements with oxygen and hydrogen

Of the groups of elements below, which are most likely to gain electrons to become anions? a. alkali metal b. boron group c. halogen d. transition metal

The big bang nucleosynthesis theory states that elements were produced in the first few minutes of the big bang while elements have their origins in the interiors of stars, forming much later in the history of the universe.

Three cards with holes are arranged in a straight line. a light is shined through the first card’s hole and travels through all three cards. what does this tell you about light rays? a) that light is reflected b) that light is refractive c) that light travels in a straight line d) that light does not travel in a straight line