Which of the following explains why elements in column 17 (the halogens) are very reactive?
their atoms contain three energy levels.
their atoms need only one electron to complete their outer energy level.
their atoms have large masses.
their atoms contain the same number of protons as electrons.

What must be true for natural selection to heppen

Need an answer asap 45 points and brainlest to the first person to answer why do scientific theories, such as biological and chemical evolution, represent the strongest explanation of the changes observed in the fossil record. must be in sentence form how can scientific theories on evolution and the fossil record change over time? must be in sentence form

Describe the two types of vascular tissue