hw 2 solutions

# 2 7 3 25 4 9 5 14 correct explanation 14 electrons

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2. 7. 3. 25. 4. 9. 5. 14. correct Explanation: 14 electrons can have this set of quantum numbers. Where = 3, seven values of m are possible, namely, 3, 2, 1, 0, - 1, - 2, and - 3. Each of these m values represents a single orbital, so there are 7 orbitals. Since each orbital can accomodate 2 electrons, 14 electrons can have this set of n and values. 008 10.0 points When n = 4, = 2 and m = - 1, to what orbital type (level) does this refer? 1. 2 p 2. 4 d correct 3. 4 p 4. 2 d Explanation: 009 10.0 points Which of the following is true? 1. An electron in a p -orbital has zero proba- bility of being found at the nucleus. correct 2. A p -orbital has a spherical boundary sur- face. 3. An s -orbital becomes more dense as the distance from the nucleus increases. 4. A 2 s orbital has one nodal plane. 5. An electron in an s -orbital has a zero probability of being found at the nucleus.

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Patel (ap29737) – Homework 2 – Sutcliffe – (50985) 3 Explanation: A node is a point, a plane or a three di- mensional region of space where the sign of the wavefunction Ψ changes from positive to negative (or negative to positive), so it equals zero. Thus the probability of finding the elec- tron there is zero. A 2 s orbital has no nodal planes, but one spherical node. All s -orbitals have a spheri- cal boundary surface, become less dense (the value of Ψ 2 decreases) as distance from the nucleus increases, and have a nonzero value of Ψ 2 at the nucleus. All p -orbitals have a dumb-bell shaped boundary surface, with two main ‘lobes’ of opposite sign, so there is a nodal plane which cuts through the nucleus; thus Ψ 2 = 0 at the nucleus. 010 10.0 points Consider the electron filling diagram be- low: 3 p ↑↓ ↑↓ 3 s ↑↓ 2 p ↑↓ ↑↓ ↑↓ 2 s 1 s ↑↓ Which of the following does it violate? I) The aufbau principle II) The Pauli exclusion principle III) Hund’s rule 1. III only 2. I and II 3. II only 4. I, II and III 5. I and III correct 6. I only 7. II and III Explanation: The half-filled 2 s subshell violates the auf- bau principle and the pairing of electrons in the 3 p subshell which still has one empty or- bital violates Hund’s rule. 011 10.0 points A neutral isolated atom has a ground state configuration of 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 7 . Identify the element. 1. phosphorus (P) 2. cobalt (Co) correct 3. argon (Ar) 4. vanadium (V) 5. The question cannot be answered unless the atomic weight is known. Explanation: Count the number of electrons by adding up the superscript of the orbitals; this gives you the atomic number. In this case that number is 27, so the element is cobalt. 012 10.0 points What is the electronic configuration of yt- trium (symbol Y)?
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