Question 1: Define noble gases and list three common elements that belong to this group.

Answer: Noble gases are inert, non-reactive elements in Group 0 of the periodic table; common elements include Helium, Neon, and Argon.

Question 2: Explain why noble gases are generally unreactive.

Answer: Because they have full outer electron shells, making them stable and unlikely to react with other elements.

Question 1: Calculate the number of atoms in 2 grams of Neon (atomic mass = 20.18 g/mol). (Use Avogadro's number, 6.022 x 10^23 mol^-1)

Answer: Number of atoms = (Mass / Atomic mass) x Avogadro's number = (2 g / 20.18 g/mol) x 6.022 x 10^23 ≈ 5.97 x 10^22 atoms

Question 2: If a container holds 22.4 liters of Helium gas at standard temperature and pressure (STP), how many moles of helium are present?

Answer: Number of moles = Volume / Molar volume at STP = 22.4 L / 22.4 L/mol = 1 mol

Question 1: Describe a safe laboratory procedure for collecting a sample of helium gas.

Answer: Use a sealed container connected to a helium source, ensure proper ventilation, wear safety goggles, and avoid inhaling large amounts of helium to prevent suffocation.

Question 2: Identify two variables that need to be controlled during an experiment to test the reactivity of noble gases.

Answer: Temperature and pressure

Question 1: A scientist observes that neon lights glow brightly in a dark room. Explain why neon emits light and how this is applied in the industry.

Answer: Neon atoms emit light when excited by an electric current, causing electrons to jump to higher energy levels and then release energy as light when returning to lower levels. This property is exploited in neon signage used in advertising and decorative lighting.

Question 2: Discuss one industrial application of argon and its importance.

Answer: Argon is used as an inert shielding gas in welding and metal fabrication, preventing oxidation and ensuring high-quality welds.