AP BIOLOGY

Detailed explanation-1: -The second shell holds 8 electrons; 2 in a 2s orbital and 6 in three 2p orbitals. The third shell holds 18 electrons; 2 in a 3s orbital; 6 in three 3p orbitals; and 10 in five 3d orbitals.

Detailed explanation-2: -The second shell has two subshells (labeled 2s and 2p). The 2s subshell holds a maximum of 2 electrons, and the 2p subshell holds a maximum of 6 electrons. This means that the second shell can hold a maximum of eight electrons (2+6=8).

Detailed explanation-3: -After the first energy level contains 2 electrons (helium), the next electrons go into the second energy level. After the second energy level has 8 electrons (neon), the next electrons go into the third energy level.

Detailed explanation-4: -Therefore, the second level can contain a maximum of eight electrons-that is, two in the s orbital and 6 in the three p orbitals. Each principal energy level above the second contains, in addition to one s orbital and three p orbitals, a set of five d orbitals, called the d sublevel.

Detailed explanation-5: -Each shell can contain only a fixed number of electrons: the first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on.