Answer:
1) B
2) D
3) D
Step-by-step explanation:
Quantum atomic theory was introduced in order to explain the behavior of subatomic particles, which could not be explained using classical physics and dynamics. Many scientists contributed to this, one of them being Heisenberg, who introduced the principle of uncertainty, stating that we can not determine the exact location and direction of motion of electron, and that there are regions of an atom in which the electrons most likely reside. These regions are called the orbitals.
Each atom consists of several energy levels (shells), depending on the number of electrons it has. They are distributed in these levels around the nucleus. Further, these levels are from the nucleus, higher the energy level is. Each shell consists of subshells, which consist of several orbitals, Each orbital has two electrons. So:
-s subshell has 1 orbital, or 1 • 2 = 2 electrons
-p subshell has 3 orbitals, or 3 • 2 = 6 electrons
-d subshell has 5 orbitals, or 5 • 2 = 10 electrons
-f subshell has 7 orbitals, or 7 • 2 = 14 electrons
etc.
When writing abbreviated or condensed electronic configuration we look up to the previous noble gas. This is used to avoid confusion and errors when writing configuration for atoms with a lot of energy levels and orbitals. We use noble gases because they are stable, inert or unreactive because their energy levels are completely filled, so we can use them as a basis on which we add excess electrons from the given atom.