How many electrons are needed for an atom to be stable

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

For the reaction shown, find the limiting reactant for each of the following initial amounts of reactants. 4al(s)+3o2(g)→2al2o3(s) a) 1 molal, 1 mol o2 b) 4 molal, 2.6 mol o2 c) 16 molal, 13 mol o2 d) 7.4 molal, 6.5 mol o2

As changes in energy levels of electrons increase, the frequencies of atomic line spectra they emit