1. 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.”


  1. 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.”


  1. In your experience, do strangers getting on a bus like to sit with other people if there is an empty seat available?
 

  1. The atomic number is equal to the number of protons in an atom.


  1. A neutral atom has the same number of electrons and protons.



  1. 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.

  1. What do you see?.
  2. Click Check. Is this electron configuration correct?



  




  1. Infer: Based on its atomic number, how many electrons does a hydrogen atom have?

  1. 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 ssubshell of the first shell.



  1. 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?




  1. Check your work: Click Check. What is the electron configuration of helium?


  1. 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:


  1. Arrange: Click Next element to select carbon. Add a second electron to the first 2p orbital.




  1. 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.




  1. Compare: How are the electrons in the 2p subshell similar to passengers getting on a bus?



  1. Practice: In the spaces below, write electron configurations for the next four elements: nitrogen, oxygen, fluorine, and neon. When you are finished, use the Gizmo to check your work. Correct any improper configurations.












  1. Apply: Atoms are most stable when their outermost shell is full. If their outermost shell is not full, atoms tend to gain, lose, or share electrons until the shell fills up. While doing this, atoms react and form chemical bonds with other atoms.


  1. Think and discuss: Select the PERIODIC TABLE tab, and look at the second row, or period, of the table. How does this row reflect the subshells of the second shell?



  




  1. Arrange: Create the correct electron configuration for argon. Then, click Next element to get to potassium (K). Click once in the first 3d orbital, and then click Check.



  1. Rearrange: As it happens, the 4s subshell is a lower-energy subshell than 3d, so it is filled first. Remove the electron from the 3d orbital and place it in the 4s orbital. Click Check. (Note: For simplicity, all but the outer shell electrons will disappear on the Bohr Model.)



  1. Arrange: Click Next element and add an electron for calcium. Click Check.


  1. Arrange: Click Next element and add an electron for scandium. Try different orbitals until you find the right one.




  1. Observe: Scandium is the first element to contain electrons in the d subshell. How many orbitals does the d subshell have, and how many electrons can fit in the dsubshell?



  1. Infer: Select the PERIODIC TABLE tab. The middle section of the table is a chemical family called the transition metals. Why do you think this section is ten columns wide?




   
  
 
  
 
 
  1. 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.


  1. Which subshell is filled after 4p?

  1. Which subshell is filled after 6s?

  1. Which subshell is filled after 5d? __________


  1. 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.)






  1. Infer: Select the PERIODIC TABLE tab. Earlier you saw that the transition metals represent the filling of the dsubshells. Now locate the purple lanthanides and actinides on the bottom rows of the periodic table.

  1. How many elements are in the in the lanthanides series?

  1. Which subshell is represented by the lanthanides family?

  1. Which subshell is represented by the actinides family?

  1. 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.”

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