Which one is incorrect?
a) Carbon is 1s^2 2s^2 3s^2
b) Sodium 1s^2 2s^2 2p^6 3s^1
c) Neon 1s^2 2s^2 2p^6
d) all are correct
I suggest you review this web page
http://www.webelements.com/webelements/elements/text/periodic-table/econ.html
and then develop a better understanding of what the elctron configurations mean. Clicking any element in that web page will take you to another page that tells you the electron configuration.
To determine which one is incorrect, we need to check the electron configurations listed for each element and compare them to the known electron configurations.
a) Carbon: The correct electron configuration for carbon is 1s^2 2s^2 2p^2. So, the electron configuration 1s^2 2s^2 3s^2 listed in option a is incorrect.
b) Sodium: The correct electron configuration for sodium is 1s^2 2s^2 2p^6 3s^1. This matches the electron configuration listed in option b.
c) Neon: The correct electron configuration for neon is 1s^2 2s^2 2p^6. This matches the electron configuration listed in option c.
Since option a contains an incorrect electron configuration, the answer is:
The incorrect option is a) Carbon is 1s^2 2s^2 3s^2.