I've been trying to do this question and I'm still stuck and don't know exactly what I'm doing wrong.
Question is: Isotope of an unknown element, X, has a mass number of 76. It has 36 electrons on this isotope and has a 2- charge. How many protons, and neutrons does the element have and what is the element?
I've tried it out and I thought the element to be Se, but it's wrong. Any help would be greatly appreciated.
36 electrons with a 2- charge means the neutral atom has 34 electrons and 34 protons, and thus 76-34 = 42 neutrons.
Looks like Selenium to me.
I'm still confused. Wouldn't there be more electrons than protons if the isotope was negatively charged?..
To solve this question, we need to understand that the atomic number of an element determines the number of protons in its nucleus. The mass number of an element is the sum of protons and neutrons in its nucleus.
Let's break down the question step by step:
1. Start with the information given: The isotope of the unknown element has a mass number of 76 and a 2- charge. This means the number of electrons is equal to the charge, so there are 36 electrons.
2. Since the isotope is neutral overall (the charge is balanced by an equal number of protons), we can conclude that the number of protons is also 36.
3. To find the number of neutrons, subtract the number of protons (36) from the mass number (76): number of neutrons = mass number - number of protons = 76 - 36 = 40.
So, the unknown element X has 36 protons and 40 neutrons.
Now, let's determine the identity of the element:
4. You mentioned that you initially guessed the element to be selenium (Se), but that answer was incorrect. To determine the correct element based on the number of protons, we can consult the periodic table.
5. By locating the element with atomic number 36, we find that it corresponds to the element Krypton (Kr).
Therefore, the unknown element X with a mass number of 76, 36 electrons, and a 2- charge is Krypton (Kr).