Question

elements in group 17 will have valence electrons.
atoms aim to have a full outer shell of electrons - usually electrons.
this desire to have 8 electrons in their outer energy level is called the
ex: carbon has how many valence electrons?
ex: chlorine has how many valence electrons?
instructions: determine the number of valence electrons in an atom of each element

1. helium
2. magnesium
3. sulfur
4. hydrogen
5. krypton
6. aluminum

Explanation:

• Helium (He): It has an atomic number of 2. Its electron configuration is \(1s^{2}\). The outermost (and only) shell (\(n = 1\)) can hold a maximum of 2 electrons. So, the number of valence electrons is 2.
• Magnesium (Mg): Atomic number is 12. Electron configuration is \(1s^{2}2s^{2}2p^{6}3s^{2}\). The outermost shell (\(n=3\)) has 2 electrons. So, the number of valence electrons is 2.
• Sulfur (S): Atomic number is 16. Electron configuration is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{4}\). The outermost shell (\(n = 3\)) has \(2 + 4=6\) electrons. So, the number of valence electrons is 6.
• Hydrogen (H): Atomic number is 1. Electron configuration is \(1s^{1}\). The outermost (and only) shell (\(n = 1\)) has 1 electron. So, the number of valence electrons is 1.
• Krypton (Kr): Atomic number is 36. Electron configuration is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^{6}\). The outermost shell (\(n = 4\)) has \(2+6 = 8\) electrons. So, the number of valence electrons is 8.
• Aluminum (Al): Atomic number is 13. Electron configuration is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{1}\). The outermost shell (\(n=3\)) has \(2 + 1=3\) electrons. So, the number of valence electrons is 3.

Answer:

1. helium: \(2\)
2. magnesium: \(2\)
3. sulfur: \(6\)
4. hydrogen: \(1\)
5. krypton: \(8\)
6. aluminum: \(3\)