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Name: ______________________________________ Date: ________________________
Student Exploration: Electron Configuration
Vocabulary: atomic number, atomic radius, Aufbau principle, chemical family, diagonal rule, electron configuration, Hund’s rule, orbital, Pauli exclusion principle, period, shell, spin, subshell
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
- Elvis Perkins, a rather shy fellow, is getting on the bus shown at right. Which seat do you think he will probably sit in? Mark this seat with an “E.”
- Marta Warren gets on the bus after Elvis. She is tired after a long day at work. Where do you think she will sit? Mark this seat with an “M.”
- In your experience, do strangers getting on a bus like to sit with other
people if there is an empty seat available? ________________________
Gizmo Warm-up Just like passengers getting on a bus, electrons orbit the nuclei of atoms in particular patterns. You will discover these patterns (and how electrons sometimes act like passengers boarding a bus) with the Electron Configuration Gizmo™.
To begin, check that Lithium is selected on the PERIODIC TABLE tab.
- The atomic number is equal to the number of protons in an atom.
How many protons are in a lithium atom? _____________
- A neutral atom has the same number of electrons and protons.
How many electrons are in a neutral lithium atom? _____________
- Select the ELECTRON CONFIGURATION tab. Click twice in the 1s box at upper left and once in the 2s box. Observe the atom model on the right.
A. What do you see? ____________________________________________________
B. Click Check. Is this electron configuration correct? _________________________
Activity A:
Small atoms
Get the Gizmo ready:
- On the PERIODIC TABLE tab, select H (hydrogen).
- Select the ELECTRON CONFIGURATION tab.
- Click Reset.
Introduction: Electrons are arranged in orbitals , subshells , and shells. These levels of organization are shown by the boxes of the Gizmo. Each box represents an orbital. The subshells are labeled with letters ( s , p , d , and f ) and the shells are labeled with numbers.
Question: How are electrons arranged in elements with atomic numbers 1 through 10?
- Infer: Based on its atomic number, how many electrons does a hydrogen atom have? _____
- Arrange: The Aufbau principle states that electrons occupy the lowest-energy orbital. Click once in the 1s box to add an electron to the only orbital in the s subshell of the first shell.
Click Check. What is the electron configuration of hydrogen? ______________________
- Arrange: Click Next element to select helium. Add another electron to the 1s orbital. The arrows represent the spin of the electron. What do you notice about the arrows?
The Pauli exclusion principle states that electrons sharing an orbital have opposite spins.
- Check your work: Click Check. What is the electron configuration of helium? ____________
- Arrange: Click Next element and create electron configurations for lithium, beryllium, and boron. Click Check to check your work, and then list each configuration below:
Lithium: _______________ Beryllium: ______________ Boron: ______________
- Arrange: Click Next element to select carbon. Add a second electron to the first 2p orbital.
Click Check. What feedback is given? __________________________________________
- Rearrange: Hund’s rule states that electrons will occupy an empty orbital when it is available in that subshell. Rearrange the electrons within the 2p subshell and click Check.
Is the configuration correct now? ______________ 1s
Show the correct configuration in the boxes at right: 2s 2p
(Activity A continued on next page)
Activity B:
Atomic radii
Get the Gizmo ready:
- On the PERIODIC TABLE tab, select Na (sodium).
- Select the ELECTRON CONFIGURATION tab.
Question: How do the radii of atoms change across a period of the periodic table?
- Predict: Positively charged protons in the nucleus of an atom are attracted to negatively charged electrons.
How do you think the atomic radii will change as electrons are added to a shell?
- Arrange: Create a proper electron configuration for sodium. After clicking Check , note the Electron configuration and the Atomic radius now listed at right.
Sodium electron configuration: _______________ Atomic radius: _________________
- Compare: Click Next element , and then add an electron to the magnesium atom. Click check, and record the electron configuration and atomic radius below.
Magnesium electron configuration: _______________ Atomic radius: _________________
- Gather data: Create electron configurations for the next six elements. Record the electron configuration and atomic radius of each. (Note: The symbol for picometer is pm .)
Element
Number of electrons
Electron configuration
Atomic radius (pm) Aluminum
Silicon Phosphorus Sulfur Chlorine Argon
- Analyze: How does the atomic radius change across a period of the periodic table?
(Activity B continued on next page)
Activity B (continued from previous page)
- Interpret: Select the ATOMIC RADIUS tab. What do you notice? ______________________
- Predict: On the ATOMIC RADIUS tab click Clear. Select the PERIODIC TABLE tab. Elements in the same column of the periodic table are called chemical families , or groups.
How do you think the size of atoms will change from top to bottom within a chemical family?
- Test: Hydrogen, lithium, and sodium are all in the same chemical family. Use the Gizmo to find the atomic radius of each, and list them below.
Hydrogen radius: ________ Lithium radius: ________ Sodium radius: ________
- Analyze: How does the atomic radius change as you go from the top to the bottom of a
chemical family? ___________________________________________________________
- Challenge: Think about the factors that control atomic radius and the patterns you’ve seen.
A. Why does the atomic radius decrease as electrons are added to a shell? _________
B. Why does the atomic radius increase as you go from the top to the bottom of a
chemical family? _____________________________________________________
- Think and discuss: Compare the electron configurations of hydrogen, lithium, and sodium. Why do you think these elements are grouped in the same family?
Activity C (continued from previous page)
- Make a rule: The diagonal rule explains which subshell will be filled next. To follow the diagonal rule, move down along an arrow until you reach the end of the arrow. Then move to the start of the next arrow to the right.
A. Which subshell is filled after 4 p? __________
B. Which subshell is filled after 6 s? __________
C. Which subshell is filled after 5 d? __________
- Practice: Determine the electron configurations of the following elements. Use the Gizmo to check your work. (Note: In some cases, the diagonal rule doesn’t work perfectly. If you submit a theoretically correct configuration, the Gizmo will give you the actual configuration.)
Element Atomic number Electron configuration
Cobalt (Co) 27 _________________________________________
Germanium (Ge) 32 _________________________________________
Yttrium (Y) 39 _________________________________________
Neodymium (Nd) 60 _________________________________________
Gold (Au) 79 _________________________________________
- Infer: Select the PERIODIC TABLE tab. Earlier you saw that the transition metals represent the filling of the d subshells. Now locate the purple lanthanides and actinides on the bottom rows of the periodic table.
A. How many elements are in the in the lanthanides series? _____________________
B. Which subshell is represented by the lanthanides family? _____________________
C. Which subshell is represented by the actinides family? _______________________
D. In general, how is the shape of the periodic table related to electron configurations? (If necessary, continue your answer on another sheet of paper.)
