Question

valence electrons & energy levels
name ____________________ period __
element quad number of valence electrons quad number of energy levels used
h

na

k

b

cl

se

ne

Explanation:

Step1: Find H's valence/levels

Hydrogen (atomic number 1): electron configuration $1s^1$. Valence electrons = 1, energy levels = 1.

Step2: Find Na's valence/levels

Sodium (atomic number 11): electron configuration $1s^22s^22p^63s^1$. Valence electrons = 1, energy levels = 3.

Step3: Find K's valence/levels

Potassium (atomic number 19): electron configuration $1s^22s^22p^63s^23p^64s^1$. Valence electrons = 1, energy levels = 4.

Step4: Find B's valence/levels

Boron (atomic number 5): electron configuration $1s^22s^22p^1$. Valence electrons = 3, energy levels = 2.

Step5: Find Cl's valence/levels

Chlorine (atomic number 17): electron configuration $1s^22s^22p^63s^23p^5$. Valence electrons = 7, energy levels = 3.

Step6: Find Se's valence/levels

Selenium (atomic number 34): electron configuration $1s^22s^22p^63s^23p^63d^{10}4s^24p^4$. Valence electrons = 6, energy levels = 4.

Step7: Find Ne's valence/levels

Neon (atomic number 10): electron configuration $1s^22s^22p^6$. Valence electrons = 8, energy levels = 2.

Answer:

Element	number of valence electrons	number of energy levels used
Na	1	2
K	1	3
B	3	2
Cl	7	3
Se	6	4
Ne	8	2