i. Nitrogen is the seventh element with a total of 7 electrons. In writing the electron configuration for nitrogen the first two electrons will go in the 1s orbital. Since 1s can only hold two electrons the next 2 electrons for N goes in the 2s orbital. The remaining three electrons will go in the 2p orbital. Therefore the N electron configuration will be 1s22s22p3.

ii. Oxygen is the eighth element with a total of 8 electrons. In writing the electron configuration for oxygen the first two electrons will go in the 1s orbital. Since 1s can only hold two electrons the next 2 electrons for O go in the 2s orbital. The remaining four electrons will go in the 2p orbital. Therefore the O electron configuration will be 1s22s22p4.

iii. In writing the electron configuration for Chlorine the first two electrons will go in the 1s orbital. Since 1s can only hold two electrons the next 2 electrons for Chlorine go in the 2s orbital. The next six electrons will go in the 2p orbital. The p orbital can hold up to six electrons. We'll put six in the 2p orbital and then put the next two electrons in the 3s. Since the 3s if now full we'll move to the 3p where we'll place the remaining five electrons. Therefore the Chlorine electron configuration will be 1s22s22p63s23p5.

Mn has an atomic number of 25. Simply use this information to obtain its electronic configuration. Mn:1s^22s^22p^63s^23p^64s^23d^5or simply[Ar]4s^23d^5.

The electronic configuration of iron (for example) is1s2 2s2 2p6 3s2 3p6 4s2 3d6 , and it is abbreviated form [Ar] 4s2 3d6