Answer:
Groups like the Halogens, which include Chlorine and Flourine, share similar properties both behaviorally and structurally. The Periodic Table is essentially a bunch of patterns and trends and the groups (like the one with Sodium and Potassium) were grouped together because of these similarities.
Explanation:
https://en.wikipedia.org/wiki/Alkali_metal
There are 5 layers. The Lithosphere, the Asthenosphere, the outer core, the inner core and the mantel.
Energy
It travels in the form of energy waves
YEs grass does have cells because it is still alive
