1 half-life - 4.5 days
x half-lives - 27 days
x=(1*27)/4.5=6
6 <span>half-lives have elapsed after 27 days.</span>
Answer:

Explanation:
Ionic bond is a bond between metals and non-metals with strong forces of attraction between charged ions.
Answer:
Four covalent bonds.
Explanation:
Hello,
In this case, given the attached picture in which you can find the Lewis dot structure for metanal (formaldehyde) we can see two C-H bonds and two C-O bonds via a double bond, thus, we can compute the type of each bond given the electronegativities of hydrogen, carbon and oxygen which are 2.1, 2.5 and 3.5 respectively:

Thus, since both electronegativity difference are less 1.7 we infer that all of them are covalent, therefore, it has four covalent bonds, two C-H bonds and a double C-O bond.
Best regards-
Answer:
What happens is,that,when a river flows into the ocean it carries some land with it. This land is made up of rocks and soil, which contains minerals. One of these minerals is Salt.
Explanation:
This is a bit long right now.
(n l m s) these are the numbers.
n=2, second orbital level.
l is the type of orbit: l=1 elongated, l=0 spherical
m=0, magnetic number: 0
s=spin, both have spin positive
You need still to round it up. Srry!