Question

q1 chemistry u2l11 electron configuration day 1
prep - work part 1: electron configuration practice
complete the ground - state orbital energy level diagrams and write the corresponding electron configurations for all of the following elements:

1. *magnesium
2. chlorine
3. **argon
4. using what you know about orbital diagrams and the beginning of the orbital diagram below, create an orbital diagram for calcium. (hint: you may need to add boxes!)

reference the models on page 3 in your student handout to answer the following questions.

1. **the lowest potential energy arrangement of electrons in an atom is called the ground state (how atoms are normally found). ground state electron configurations can be predicted by a strict set of rules; one is known as the aufbau principle (\aufbau\ means filling up). examine the diagrams in the model and the statements below to determine the phrase that best describes each rule. circle the correct answer.

a. *based on where a single electron is placed, the lowest potential energy electron in an atom is found in the ______ sublevel.
1s 2s 3s

Explanation:

Step1: Recall atomic numbers

Magnesium has an atomic number of 12, Chlorine has 17, Argon has 18 and Calcium has 20. The number of electrons is equal to the atomic number for neutral atoms.

Step2: Apply Aufbau principle for Magnesium

Electrons fill orbitals in order of increasing energy. For Mg (12 electrons), the electron - configuration is $1s^{2}2s^{2}2p^{6}3s^{2}$. In the orbital - energy level diagram, the 1s orbital has 2 electrons (paired), 2s has 2 electrons (paired), 2p has 6 electrons (3 pairs) and 3s has 2 electrons (paired).

Step3: Apply Aufbau principle for Chlorine

For Cl (17 electrons), the electron - configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}$. In the orbital - energy level diagram, 1s has 2 electrons (paired), 2s has 2 electrons (paired), 2p has 6 electrons (3 pairs), 3s has 2 electrons (paired) and 3p has 5 electrons (1 pair and 3 unpaired).

Step4: Apply Aufbau principle for Argon

For Ar (18 electrons), the electron - configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}$. In the orbital - energy level diagram, 1s has 2 electrons (paired), 2s has 2 electrons (paired), 2p has 6 electrons (3 pairs), 3s has 2 electrons (paired) and 3p has 6 electrons (3 pairs).

Step5: Apply Aufbau principle for Calcium

For Ca (20 electrons), the electron - configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}$. In the orbital - energy level diagram, 1s has 2 electrons (paired), 2s has 2 electrons (paired), 2p has 6 electrons (3 pairs), 3s has 2 electrons (paired), 3p has 6 electrons (3 pairs) and 4s has 2 electrons (paired).

Step6: Answer question 8a

According to the Aufbau principle, the lowest potential energy electron in an atom is found in the 1s sublevel as it has the lowest energy among the sublevels.

Answer:

Magnesium: Electron - configuration: $1s^{2}2s^{2}2p^{6}3s^{2}$, Orbital - energy level diagram: 1s (2 paired electrons), 2s (2 paired electrons), 2p (3 pairs of electrons), 3s (2 paired electrons)
Chlorine: Electron - configuration: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}$, Orbital - energy level diagram: 1s (2 paired electrons), 2s (2 paired electrons), 2p (3 pairs of electrons), 3s (2 paired electrons), 3p (1 pair and 3 unpaired electrons)
Argon: Electron - configuration: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}$, Orbital - energy level diagram: 1s (2 paired electrons), 2s (2 paired electrons), 2p (3 pairs of electrons), 3s (2 paired electrons), 3p (3 pairs of electrons)
Calcium: Electron - configuration: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}$, Orbital - energy level diagram: 1s (2 paired electrons), 2s (2 paired electrons), 2p (3 pairs of electrons), 3s (2 paired electrons), 3p (3 pairs of electrons), 4s (2 paired electrons)
8a: 1s