Any living organism which is "in danger of extinction throughout all or a significant portion of its range.
This wac formerlv used as a refriaerant and as a nronellant in aerosol cans These

each chemical family is represented as a group or column on the periodic table. based on chemical properties, there are 6 types of chemical families. group 1 represents alkali metals, group 2 represents alkaline earth metals, groups 3 to 12 represent transition metals, groups 13 to 16 represent non-metals and other metals, group 17 represents halogens and group 18 represents noble gases.

the answer is symmetrical : )