Question

question 1 of 7
identify the number of core and valence electrons for each atom.
ar: core electrons ar: valence electrons
ca: core electrons ca: valence electrons
f: core electrons f: valence electrons

Explanation:

Step1: Determine the atomic number of each element

• The atomic number of Ar (argon) is 18.
• The atomic number of Ca (calcium) is 20.
• The atomic number of F (fluorine) is 9.

Step2: Recall the electron - configuration rules

• Core electrons are the electrons in an atom that are not valence electrons. Valence electrons are the electrons in the outermost shell of an atom.
• For Ar: Its electron configuration is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}\). The valence shell is the third shell (\(n = 3\)). The number of valence electrons is 8 (\(3s^{2}+3p^{6}\)). The number of core electrons is \(18 - 8=10\)
• For Ca: Its electron configuration is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}\). The valence shell is the fourth shell (\(n = 4\)). The number of valence electrons is 2 (\(4s^{2}\)). The number of core electrons is \(20 - 2 = 18\)
• For F: Its electron configuration is \(1s^{2}2s^{2}2p^{5}\). The valence shell is the second shell (\(n=2\)). The number of valence electrons is 7 (\(2s^{2}+2p^{5}\)). The number of core electrons is \(9 - 7=2\)

Answer:

Ar: 10 core electrons, 8 valence electrons
Ca: 18 core electrons, 2 valence electrons
F: 2 core electrons, 7 valence electrons