Out of 500 silicon atoms: 460 are si-28, which has a mass of 27.98 amu 25 are si-29, which has a mass of 28.98 amu and 15 are si-30, which has a mass of 29.97 amu. what is the average atomic mass of silicon? (round to 2 decimal places) (hint: they did not give you percentages, but you can calculate the percentages and then do the problem)

The atomic radius of sodium is 186 pm and of chlorine is 100 pm. the ionic radius for na+ is 102 pm and for cl– is 181 pm. in going from na to cl in period 3, why does the atomic radius decrease while the ionic radius increases? a. the inner electrons in the sodium cation shield its valence electrons more effectively than the inner electrons in the chloride anion do. b. the inner electrons shield the valence electrons more effectively in the chlorine atom than in the chloride anion. c. the outermost electrons in chloride experience a smaller effective nuclear charge than those in the sodium cation do. d. the outermost electrons in chloride experience a larger effective nuclear charge than those in the sodium cation do. e. monatomic ions are bigger than the atoms from which they are formed.

Use examples from the article to explain one positive and one negative effect that chemistry has had on society.

What will most likely happen when two bromine atoms bond together?