Answer:
The part that completes the nuclear equation is:
[tex]^{221}_{87}Fr[/tex]
Explanation:
A) Preliminar explanation
The nuclear equation represents a nuclear reaction: the change of the nucleus of an atom.
The given equation represents an actinium atom releasing an alpha particle.
This is the meaning of each part of the equation:
- Ac is the chemical symbol of actinium
- The superscript to the left of the chemical symbol is the mass number of the atom (number of protons plus number of neutrons). The mass number is 225.
- The subscript to the left of the chemical symbol is the atomic number of the atom (number of protons). The atomic number is 89.
- [tex]^4_2He[/tex] is the symbol of the alpha particle. It is an atom of helium
- The mass number is 4
- The atomic number is 2
B) Solution
To complete the nuclear equation you must do two balances: mass number balance and atomic number balance.
i) Mass number balance
- 225 = A + 4 ⇒ A = 225 - 4 = 221
ii) Atomic number balance
- 89 = Z + 2 ⇒ Z = 89 - 2 = 87
Therefore, the mass number of the unknown atom is 221, and the atomic number is 87.
From a periodic table, the element with atomic number 87 is francium, Fr.
Now, you have the chemical symbol, the atomic number, and the mass number of the unknown atom, which lets you to write the atom that completes the nuclear equation.
[tex]^{221}_{87}Fr[/tex]
