Answer:
d. Radon-222
Explanation:
²²⁶₈₈Ra → ²²²₈₆Rn + ⁴₂He
Alpha particle is a helium nucleus with mass number 4 and atomic number 2. According to the law of conversation of mass, the sum of the mass number and atomic number must be equal on both side of the reaction.
Since the mass number of Ra is 226 and that of He is 4. The mass number of the unknown element must be 226 - 4 = 222.
Since the atomic number of Ra is 88 and that of He is 2. The atomic number of the unknown element must be 88 - 2 = 86.
Now looking in the periodic table Radon is the only element with atomic number 86.
Answer: 16.32 g of 
as excess reagent are left.
Explanation:
To calculate the moles :
According to stoichiometry :
2 moles of 
require = 1 mole of
Thus 0.34 moles of will require=
of
Thus is the limiting reagent as it limits the formation of product and is the excess reagent.
Moles of left = (0.68-0.17) mol = 0.51 mol
Mass of 
Thus 16.32 g of as excess reagent are left.
Answer:
the answer is C4H10 I hope I helped
Answer:
When an atom gains or loses energy, the energy of an electron can change.
An electron in an atom can move from one energy level to another when the atom gains or loses energy.
Explanation:
The possible energies that electrons in an atom
can have are called energy levels.
• An electron cannot exist between energy levels.
https://1.cdn.edl.io/tTlW7xRtvD62xSe7RcZlJr7kSR7XsL93akcgJkbGJBNNcpwY.pdf
*this link can also help* brainly ist plz
