A layer above the earth that protects the planet from dangerous UV that are sent from the sun
Alkali metals have only one electron in their outermost energy levels , so (they can loose one electron to) they form a mono positive ion only . That's why alkali metal do not from dispositive ions .
Hope that helps:)
The units on the ruler are inches, centimeters, and millimeters. Nanometers (nm) is equivalent to 10^-9 m. Each graduation on the ruler represents 0.1 millimeters or 0.01 centimeters. The other side also has a graduation of 0.1 inch. The function of the ruler depends on how you use it.
