How many electrons are contained in an ion formed from an atom of Cs? How many electrons are contained in an ion formed from an atom of Se
The Correct Answer and Explanation is:
Correct Answers:
- An ion formed from a Cs (cesium) atom contains 54 electrons.
- An ion formed from a Se (selenium) atom contains 36 electrons.
Explanation:
To determine the number of electrons in an ion formed from a given atom, you must first understand the atomic number of the element and how it behaves when forming ions.
1. Cesium (Cs):
Cesium has an atomic number of 55, which means a neutral cesium atom contains 55 protons and 55 electrons.
Cesium is an alkali metal and is located in Group 1 of the periodic table. Atoms in this group tend to lose one electron to achieve a stable electron configuration similar to the nearest noble gas (xenon in this case).
When cesium loses one electron, it forms a Cs⁺ ion.
- The number of protons remains the same (55).
- It loses one electron, so it now has 55 – 1 = 54 electrons.
Therefore, a Cs⁺ ion contains 54 electrons.
2. Selenium (Se):
Selenium has an atomic number of 34, so a neutral selenium atom has 34 protons and 34 electrons.
Selenium is a nonmetal located in Group 16. Atoms in this group tend to gain two electrons to complete their outer shell and resemble the noble gas krypton.
When selenium gains two electrons, it forms a Se²⁻ ion.
- The number of protons remains at 34.
- It gains two electrons, so it now has 34 + 2 = 36 electrons.
Thus, a Se²⁻ ion contains 36 electrons.
In conclusion:
- Cs forms a positive ion (cation) by losing one electron, resulting in 54 electrons.
- Se forms a negative ion (anion) by gaining two electrons, resulting in 36 electrons.
