Question

question 6 of 32 which element has 2 valence electrons in the 2s sublevel? the periodic table a. li b. c c. be d. he

Explanation:

Step1: Analyze Li electron - configuration

Li (lithium) has an atomic number of 3. Its electron - configuration is $1s^{2}2s^{1}$, so it has 1 valence electron in the 2s sublevel.

Step2: Analyze C electron - configuration

C (carbon) has an atomic number of 6. Its electron - configuration is $1s^{2}2s^{2}2p^{2}$, but its valence electrons are in both 2s and 2p sublevels, not just 2 valence electrons in the 2s sublevel.

Step3: Analyze Be electron - configuration

Be (beryllium) has an atomic number of 4. Its electron - configuration is $1s^{2}2s^{2}$. It has 2 valence electrons in the 2s sublevel.

Step4: Analyze He electron - configuration

He (helium) has an atomic number of 2. Its electron - configuration is $1s^{2}$. It does not have electrons in the 2s sublevel.

Answer:

C. Be