What is another element that will have the same valence electrons as Be and Ca?

A__ is two or more substances that are together in the same place but are not chemically combined

In as 1°, 2°, 3°, or 4°. be to . : °b: °c: °d: ° : °b: °c: °d: ° : °b: °c: °d: °e: °f: °g: °h: ° : °b: °c: °d: °e: °f: °g: °h: °i: °

If a sample of radioactive isotopes takes 600 minutes to decay from 400 grams to 50 grams, what is the half-life of the isotope?