Domain bacteria, Domain Archaea and Domain Eucarya
The lacrimal<span> glands secrete tears which act to lubricate and protect the cornea and eyeball from injury which may result from small particles such as dust. Tears are a watery fluid with an electrolyte content similar to that of plasma and contains: bactericidal enzymes known as lysozyme and lactoferrin.</span>
Gene flow does not promote speciation, whereas season of fertility, natural selection, and genetic drift do.
Answer:
1. Magnesium and oxygen atoms bond to form an ionic compound; this is evident because one forms a cation and the other an anion. When an ionic compound is formed, one atom "steals" an electron (or electrons) from another. In this case, an oxygen atom (which is pretty electronegative by the way) "steals" 2 electrons from a magnesium atom. The resulting oxygen anion and magnesium cation attract one another to form a bond (more specifically, an ionic one).
2. The oxygen atom needed two sodium atoms to bond because it needs two additional electrons to achieve a stable octet of electrons. 1 sodium atom provides 1 additional electron after it is "stolen" by oxygen, so 2 sodium atoms are needed in total to form the bond.
3. The magnesium atom needed two fluorine atoms to bond because it needs to lose two electrons to achieve a stable configuration/octet of electrons. 1 fluorine atom "steals" one electron, so 2 are needed in total.
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