Ionic compounds are made of ions- charges. In LiF and NaCl, the first element has a +1 and the second element has a charge of -1. Elements that are +1 are alkali metals and elements that are -1 are halogens. Noble gases have full octets in their outermost valence shell, and since they're full it's so stable so it doesn't react with anything.
Answer:humans have put ridiculous amounts of carbon dioxide into the atmosphereThese events are linked to the mass burning of fossil fuels to meet an increase in human demand