What is the symbol for the entity that has 17 protons, 20 neutrons, and 18 electrons?
The Correct Answer and Explanation is :
The entity with 17 protons, 20 neutrons, and 18 electrons is chlorine (Cl), specifically the isotope chlorine-37 (Cl-37).
Explanation:
- Protons and the Atomic Number:
The number of protons in an atom determines its atomic number and thus its identity on the periodic table. In this case, the atom has 17 protons, so it must be chlorine (Cl), because chlorine has an atomic number of 17. This is true for all chlorine atoms, regardless of the isotope. - Neutrons and Isotopes:
Neutrons contribute to the mass of the atom but do not affect its chemical properties. The number of neutrons in this atom is given as 20. To find the isotope, you add the number of protons (17) and neutrons (20) together:
[
\text{Mass number} = 17 \, (\text{protons}) + 20 \, (\text{neutrons}) = 37
]
Therefore, the isotope is chlorine-37 (Cl-37). - Electrons and Charge:
The number of electrons in an atom typically equals the number of protons if the atom is neutral. However, in this case, the atom has 18 electrons, which is one more than the 17 protons. This indicates that the atom is an anion (a negatively charged ion) with a -1 charge. The extra electron gives the atom a net negative charge. - Symbol:
The symbol for chlorine-37, considering the charge, would be written as:
[
\text{Cl}^{-}
]
This shows that it is a chlorine atom with 17 protons, 20 neutrons, and 18 electrons, and it carries a single negative charge.
In summary, the correct symbol for this entity is Cl⁻ (chlorine-37 anion). The chlorine atom in this case is negatively charged because it has one more electron than protons, making it an anion.