Read the labels of several commercial products and identify monatomic ions of at least six main group elements contained in the products. Write the complete electron configurations of these cations and anions.
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Chemistry 2e · 6.4 Electronic Structure of Atoms (Electron Configurations)
Electron configurations: practice problems
10 problems from the book, with its answers. Check your working, or have any of them explained to you on the whiteboard.
How to approach these problems
Fill subshells in order of energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, and so on; reading the periodic table row by row gives the same order. An s subshell holds 2 electrons, p 6, d 10 and f 14, and the superscripts must add up to the atomic number. In an orbital diagram, put one electron in each orbital of a subshell before pairing any (Hund's rule). For an ion, start from the neutral atom and add or remove electrons: a transition metal loses its 4s electrons before its 3d ones. The usual mistakes: filling 3d before 4s, forgetting the ion's charge, and missing the exceptions of chromium and copper (3d⁵4s¹ and 3d¹⁰4s¹).
Exercises 49
Using complete subshell notation (1s²2s²2p⁶, and so forth), predict the electron configuration of each of the following atoms:
(a) N
(b) Si
(c) Fe
(d) Te
(e) Tb
Exercises 51
What additional information do we need to answer the question “Which ion has the electron configuration 1s²2s²2p⁶3s²3p⁶”?
Exercises 53
Use an orbital diagram to describe the electron configuration of the valence shell of each of the following atoms:
(a) N
(b) Si
(c) Fe
(d) Te
(e) Mo
Exercises 55
Which atom has the electron configuration 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d²?
Exercises 57
Which ion with a +1 charge has the electron configuration 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶? Which ion with a –2 charge has this configuration?
Exercises 59
Which of the following has two unpaired electrons?
(a) Mg
(b) Si
(c) S
(d) Both Mg and S
(e) Both Si and S.
Exercises 61
Which atom would be expected to have a half-filled 4s subshell?
Exercises 63
Thallium was used as a poison in the Agatha Christie mystery story “The Pale Horse.” Thallium has two possible cationic forms, +1 and +3. The +1 compounds are the more stable. Write the electron structure of the +1 cation of thallium.
Exercises 65
Cobalt–60 and iodine–131 are radioactive isotopes commonly used in nuclear medicine. How many protons, neutrons, and electrons are in atoms of these isotopes? Write the complete electron configuration for each isotope.
Key terms · 7
- Aufbau principle
- procedure in which the electron configuration of the elements is determined by “building” them in order of atomic numbers, adding one proton to the nucleus and one electron to the proper subshell at a time
- core electron
- electron in an atom that occupies the orbitals of the inner shells
- electron configuration
- listing that identifies the electron occupancy of an atom’s shells and subshells
- Hund’s rule
- every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin
- orbital diagram
- pictorial representation of the electron configuration showing each orbital as a box and each electron as an arrow
- valence electrons
- electrons in the high energy outer shell(s) of an atom
- valence shell
- high energy outer shell(s) of an atom
Learn 6.4 on the whiteboard
The tutor teaches the whole section, drawing it out step by step and answering your questions as you go.