Here are the answers to your questions regarding elements in Period 3:
1.1 Give the element that has the largest atomic radius in Period 3.
Answer: Sodium (Na)
1.2 Sodium is a reactive metal.
1.2.1 Describe one physical property of sodium.
Answer: Sodium is a soft metal that can be easily cut with a knife.
1.2.2 Write down the electronic configuration of the sodium ion.
Answer: The electronic configuration of the sodium ion (Na⁺) is 1s².
1.2.3 Give one observation when sodium reacts with cold water.
Answer: Sodium fizzes and floats on the surface of water while forming bubbles of hydrogen gas.
1.2.4 State the flame colour of sodium.
Answer: The flame colour of sodium is bright yellow.
1.3 Magnesium reacts slowly with warm water to form a base, magnesium hydroxide.
1.3.1 Define a base in terms of proton transfer.
Answer: A base is a substance that accepts protons (H⁺ ions) in a chemical reaction.
1.3.2 Suggest the pH of magnesium hydroxide and give the colour of universal Indicator.
Answer:
pH: Approximately 10-11
Colour of universal indicator: Blue to purple
1.3.3 Magnesium hydroxide can be used to treat indigestion by reacting with stomach acid. State the type of reaction this is.
Answer: This is a neutralization reaction.
1.4 Aluminium combines with oxygen to form aluminum oxide. Name the type of oxide aluminium oxide forms.
Answer: Aluminium oxide forms an amphoteric oxide.
1.5 Silicon dioxide has a giant structure.
1.5.1 Name the type of bonding in silicon dioxide.
Answer: The type of bonding in silicon dioxide is covalent bonding.
1.5.2 Give one physical property of silicon dioxide.
Answer: Silicon dioxide is hard and has a high melting point.
Feel free to ask if you need further clarification or additional questions!