Answer:
+2
Explanation:
Oxygen ions always have the charge of -2. Since Fe is in the transition metal stage, it doesn't have a specific set of ions unless specifically shown. In the equation FeO, we would have to have a +2 charge when equalling the two atoms together. So when combines the charges would look like:

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Atmosphere is the envelope of air that surrounds the earth.
Answer:
Electronegativity = 1.87.
Ionic radius = 109 pm.
Atomic radius = -39 pm
First ionization energy = 410 kJ/mol
Explanation:
Hello!
In this case, since electronegativity, ionic radius, atomic radius and first ionization energy are periodic properties that have specific trends, we can summarize it by realizing that oxygen and beryllium belong the same period 2 and differ in group, 6A and 2A respectively.
In such a way, the required comparison is written below:
Electronegativity = 3.44 (oxygen) - 1.57 (beryllium) = 1.87.
Ionic radius = 140 pm (oxygen)- 31 pm (beryllium) = 109.
Atomic radius = 73 pm (oxygen) - 112 pm (beryllium) = -39 pm
First ionization energy = 1310 kJ/mol (oxygen) - 900 kJ/mol (beryllium) = 410 kJ/mol
It means that electronegativity, ionic radius and first ionization energy increases from left to right whereas the atomic radius from right to left.
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Answer:
Explanation: in exothermic reaction heat is released out
In endothermic reaction heat is absorbed