Answer:
the ionic radius of the anion 
Explanation:
From the diagram shown below :
The anion
is located at the corners
The cation
is located at the body center
The Body diagonal length = 
∴ 
Given that :
(i.e the ratio of the ionic radius of the cation to the ionic radius of
the anion )

Also ; a = 664 pm
Then :

Therefore, the ionic radius of the anion 
Answer:
A)21
Explanation:
To know the difference between the number of electrons in the two atoms, we must first know the number of electrons in the atoms.
For Selenium, Se, we have 34 electrons. The element is in group 6 on the periodic table.
Aluminum on the other hand is in the Boron family with a total of 13 electrons.
The difference,( 34-13) electrons gives a total of 21 electrons
Answer:
157.8 g
Explanation:
Step 1: Write the balanced equation
Fe₂O₃ + 3 CO ⟶ 3 CO₂ + 2 Fe
Step 2: Calculate the moles corresponding to 209.7 g of Fe
The molar mass of Fe is 55.85 g/mol
209.7 g × 1 mol/55.85 g = 3.755 mol
Step 3: Calculate the moles of CO needed to produce 3.755 moles of Fe
The molar ratio of CO to Fe is 3:2. The moles of CO needed are 3/2 × 3.755 = 5.633 mol
Step 4: Calculate the mass corresponding to 5.633 moles of CO
The molar mass of CO is 28.01 g/mol.
5.633 mol × 28.01 g/mol = 157.8 g
Answer:
all these are physical properties except release of heat so it's probably heat energy given off