1. There are 15 electrons which means that the element is phosphorus. We know it is in the excited state because an electron from the second ring has moved to the third one, typically it would be 2 - 8 - 5.
2. An element with 3 valence electrons will be 3 spaces from the left side of the periodic table. Sodium is 1, Magnesium is 2, Aluminium is 3, and Silicon is 4. Noble gasses on the right have all 8.
