Question

noble gases - complete outer shells (8 valence electrons w/ 1 exception)

1. poor hydrogen! why is it an exception to the family on which it rides atop? hydrogen is certainly not a metal! do you need to repair # 8? how would you classify h? explain:
2. using a real periodic table and the ideas from your model predict the number of valence electrons for:

barium
lead
xenon
potassium
carbon
lead
iodine

1. explain how you know the above is true:

Explanation:

Question 9:

Step1: Recall Hydrogen's Properties

Hydrogen has 1 proton, 1 electron. Its electron configuration is \(1s^1\). Metals typically lose electrons, non - metals gain, but H can do both (e.g., \(H^+\) or \(H^-\) in compounds like \(HCl\) and \(NaH\)). Noble gases have full outer shells (\(ns^2np^6\) for period 2+), H has 1 valence electron, not full. Metals are usually solid (except Hg), conductive, malleable. H is a gas, non - malleable, non - conductive as a gas.

Step2: Explain Exception to Family

Hydrogen is often placed above Group 1 (alkali metals) because it has 1 valence electron (like Group 1: \(ns^1\)). But it's not a metal: alkali metals are metals (solid, conductive, lose 1e⁻ easily), H is a gas, doesn't have metallic properties (e.g., no metallic luster, not malleable). It can also act like a non - metal (gain 1e⁻ to form \(H^-\) as in \(NaH\)), unlike Group 1 metals which only lose electrons.

Step3: Classify Hydrogen

Hydrogen is a non - metal (or a unique element). It's a diatomic gas (\(H_2\)) at STP, forms covalent bonds (e.g., \(H_2O\)) or ionic bonds as \(H^-\) (less common), but doesn't exhibit metallic behavior.

Step1: Noble Gases

Noble gases (except He) have 8 valence electrons (full outer shell: \(ns^2np^6\)). He has 2, which is a full shell for \(n = 1\) (\(1s^2\)). This is confirmed by electron configuration (e.g., Ne: \(1s^22s^22p^6\), Ar: \(1s^22s^22p^63s^23p^6\)).

Step2: Valence Electrons in Q10

For the elements in Q10:

• Lead (Group 14): Group number (14) - 10 (for main - group elements, valence electrons = Group number - 10 for Groups 13 - 18) → \(14 - 10=4\).
• Xenon (Group 18): Group 18, so 8 valence electrons (full shell).
• Potassium (Group 1): Group 1, so 1 valence electron.
• Carbon (Group 14): \(14 - 10 = 4\) valence electrons.
• Iodine (Group 17): \(17 - 10 = 7\) valence electrons.
• Barium (Group 2): Group 2, so 2 valence electrons.

These match the electron configuration rules (e.g., Group 1: \(ns^1\), Group 2: \(ns^2\), Groups 13 - 18: \(ns^2np^{1 - 6}\)) and the periodic table's group - valence electron relationship.

Answer:

Hydrogen is an exception to Group 1 (alkali metals) because it has 1 valence electron (like Group 1) but lacks metallic properties (e.g., not a solid metal, no metallic conductivity/malleability). It's not a metal as it's a gas, non - malleable, and can gain or lose electrons (unlike Group 1 metals which only lose). It can be classified as a non - metal (or a unique element).

Question 10:

To find valence electrons, we use the periodic table:

• Lead (Pb): Group 14. Valence electrons = 4 (Group 14: \(ns^2np^2\), total 4 valence e⁻).
• Xenon (Xe): Group 18 (noble gases). Valence electrons = 8 (full outer shell: \(ns^2np^6\)).
• Potassium (K): Group 1. Valence electrons = 1 (Group 1: \(ns^1\)).
• Carbon (C): Group 14. Valence electrons = 4 (same as Lead, Group 14 has 4 valence e⁻).
• Iodine (I): Group 17. Valence electrons = 7 (Group 17: \(ns^2np^5\), 7 valence e⁻).
• Barium (Ba): Group 2. Valence electrons = 2 (Group 2: \(ns^2\)).