【Daily Question】Theoretical Foundation 2020.06.17
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Multiple-choice question: An element has one electron in its outermost atomic orbital, the 4s orbital. Which of the following sets of four quantum numbers represents this electron correctly? A. (4,0,1,+1/2) B. (4,1,0,-1/2) C. (4,0,0,+1/2) D. (4,1,1,-1/2) Answer: C. Hint: Those who can explain the reasoning behind the solution will receive an additional reward; the answer can be found in the response
C.(4.0,0,+1/2)
C. Principal quantum number n: It indicates the distance of an atomic orbital from the nucleus and determines the energy of that atomic orbital. The larger n, the higher the orbital energy. n is also known as the electron shell; each electron shell can hold a maximum of 2n electrons. Angular momentum quantum number l: It determines the shape of atomic orbitals and is also a factor that influences the energy of multi-electron atomic orbitals. When the value of n is fixed, l can take the values 0, 1, 2, 3, 4, …… (n–1). Numerically, l < n. s p d f g…… When n and l have the same values, the electrons have the same energy. Magnetic quantum number m: determines the direction of the atomic orbital. When the value of l is fixed, m can take on the values 0, ±1, ±2, ±3……±l. Numerically, m ≤ l. The spin quantum number m describes the spin state of an electron; its possible values are m = ±1/2 or “↑↓”. The values of quantum numbers are mutually constrained, thus allowing it to be determined how many electron motion states can exist in each electron shell. The motion state of each electron can be described by four quantum numbers. There are no two electrons in an atom with exactly the same four quantum numbers, a principle known as the Pauli exclusion principle.