Question

activity a: small atoms
introduction: electrons are shown arranged in orbitals, subshells are labeled with letters (s, p, d, and f) and the box represents an orbital. the boxes in the gizmo are labeled with numbers 1 through 18.
question: how are electrons arranged in elements with atomic numbers 1 through 18?

1. arrange: the aufbau principle states that electrons occupy the lowest - energy orbital available. when hydrogen is selected, the orbital is arranged once in the 1s box from bottom to top. click once in the 1s box to add an electron to the only orbital in the first shell. what is the electron configuration of hydrogen?
2. 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? 2 electrons in 1s orbital are opposite.
3. check your work: click check. what is the electron configuration of helium? 1s²
4. 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: 1s²2s¹
beryllium: 1s²2s²
boron: 1s²2s²2p¹

1. arrange: click next element to select carbon. add a second electron to the first 2p orbital. click check. what feedback is given?
2. 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? show the correct configuration in the boxes at right.

Explanation:

Step1: Recall electron - filling rules

Electrons fill orbitals according to the Aufbau principle, Pauli exclusion principle, and Hund's rule.

Step2: Analyze carbon's electron configuration

Carbon has 6 electrons. The first 2 fill the 1s orbital ($1s^2$), the next 2 fill the 2s orbital ($2s^2$), and the remaining 2 electrons should be placed in the 2p orbitals following Hund's rule.

Step3: Apply Hund's rule for carbon

Hund's rule states that electrons will occupy empty orbitals in the same sub - shell before pairing up. So for carbon ($1s^22s^22p^2$), the 2p electrons should be in separate 2p orbitals with parallel spins.

Step4: Answer question 5

When a second electron is added to the first 2p orbital in an incorrect way (violating Hund's rule), the feedback is likely that the electron configuration is incorrect and electrons should be placed in separate 2p orbitals first.

Step5: Answer question 6

After rearranging the electrons in the 2p sub - shell according to Hund's rule, the configuration is correct. The correct configuration in box form: 1s has 2 electrons (represented by 2 arrows in one box), 2s has 2 electrons (2 arrows in one box), and 2p has 2 electrons with parallel spins in two separate boxes out of three.

Answer:

1. The feedback is that the electron - filling violates Hund's rule and electrons should occupy separate 2p orbitals before pairing up.
2. Yes, the configuration is correct now. The correct configuration in box form: 1s: two arrows in one box, 2s: two arrows in one box, 2p: one arrow in each of two separate boxes.