Explain why not all microbes are harmful.

All the microbial activities and products are not harmful for humans. Hence all microbes are not harmful.

Explanation:

There are 2 types of microbes present around us- good microbes and bad microbes. The goodness and badness of microbes depend upon their activities. There are several viruses and bacteria which cause different diseases in the human body. At the same time, there are other kinds of microbes which are good for us.

The E.coli bacteria in our gut maintains the normal flora of our intestine and maintains a symbiotic relationship. The beneficial microbes maintain symbiotic with the host and their microbial products are useful.  

For example,  yeast is used in making cakes, breads, biscuits. The yeast powder is used for these purposes. Some microbial fermentation products are edible to humans. The lactobacillus bacteria help in the curdling of milk. Many antibiotics used for us comes from microbial activities. These are the reasons all the microbes are not harmful.

allowed for the prediction of the properties of missing elements.

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.