Final answer:
The atom with the highest electronegativity among the provided options is non-metal oxygen, atomic number 8, due to its position in the upper right corner of the periodic table, where electronegativity values are the highest.
Step-by-step explanation:
To identify the atom that is likely to have the highest electronegativity, we need to consider their positions in the periodic table and the general trend of electronegativity increasing from left to right across a period, and decreasing down a group. Looking at the options provided:
- Beryllium, atomic number 4, is an alkaline earth metal and would not have the highest electronegativity.
- Magnesium, atomic number 12, another alkaline earth metal, also has a relatively low electronegativity.
- Selenium, atomic number 34, is a non-metal and is positioned towards the upper right section of the periodic table, indicating it would have higher electronegativity than the metals listed.
- Oxygen, atomic number 8, is a non-metal as well, and it's found even further to the right on the periodic table compared to selenium, suggesting it would have an even higher electronegativity.
Considering the mentioned elements, non-metal oxygen, atomic number 8, is likely to have the highest electronegativity since it is located farthest to the right and up towards the top on the periodic table.