What is the chemical symbol for the element with electron configuration 2,4?

• A. C
• B. N
• C. O
• D. Be

Answer: (A)

Understanding electron shells helps you connect a simple count to the element’s identity. Interpreting 2,4 means the first energy level contains 2 electrons (the 1s orbital), and the second energy level contains 4 electrons (2s2 and 2p2). That sums to 6 electrons in total, so the atomic number is 6. The element with atomic number 6 is carbon, whose symbol is C.

Other elements would have different distributions in the second shell: for example, beryllium is 2,0; boron is 2,3; nitrogen is 2,5; and oxygen is 2,6. None match 2,4, so carbon is the correct symbol.