For #1, I'd say it's "It will usually bond to multiple atoms which can provide a total of 4 additional electrons."
2. Ionic (I'm quite certain because anions/cations (-1 & +1) are Ionic from what I recall, if that's true it's Ionic.
3. "comparison of the associated families to which the elements belong" and
"the difference in electronegativities" are what I would choose, as I mentioned in a comment earlier.
If I'm wrong let me know, but I am at least 80% sure that these responses are correct from what I remember in Chemistry.
The temperature decreases because there is no ozone in the mesosphere and the amount of air is decreasing.
Answer:
Answer: medium level profession can be defined as some one who has moved past entry level but isn't nearing the end . whereas high level profession means a person has moved past entry level and also has reached the end.
Answer:
A chemical reaction.
Explanation:
A change in temperature is evidence of a chemical reaction.
Also: They are chemicals...
The green and black symbols refer to atoms, that make up the molecule of water, more specifically you can say that the 2 Hydrogen atoms are the black ones found outside, while the central atom, that is also green would be oxygen.