How would you explain to an elementary school student what the periodic table is?

Which of the following is a compound? a.carbon b.oxygen c.hydrogen d.water

Cucl2 + 2nano3 cu(no3)2 + 2nacl what is the percent yield of nacl if 31.0 g of cucl2 reacts with excess nano3 to produce 21.2 g of nacl? 49.7% 58.4% 63.6% 78.7%

What is the polyatamic ion of borate