The answer is b. radon-222. The alpha decay means that it will emit an alpha particle when decays. The alpha particle has two protons and two neutrons. So Radium(88) minus two protons will become Radon(86). And the atomic mass will become 226-4=222.
Answer:
all the elements in the same period have the same valence electrons.
Answer:
formula units of sodium chloride can be formed from 13.0 gram of ferric chloride.
Explanation:
Mass of ferric chloride = 13.0 g
Moles of ferric chloride = 
1 mole of ferric chloride has three moles of chloride ions.Then 0.08 moles of ferric chloride will have :
of chloride

1 mole of sodium ion reacts with 1 mole of chloride ion to form 1 mole of NaCl. Then 0.24 moles of chloride ion will give:
of NaCl
1 mole =
molecules/ atoms
Number of NaCl molecules in 0.24 moles :

formula units of sodium chloride can be formed from 13.0 gram of ferric chloride.