Answer:
If the earring is still gold it is a physical change.
Explanation:
Melting something can be a chemical change but since the gold is still gold its physical. Physical actions, such as changing temperature or pressure, can cause physical changes. No chemical changes took place when you melted the ice. The water molecules are still water molecules.
Chlorine gas reacts vigorously with hydrogen gas to form hydrogen chloride. It is commonly known as hydrochloric acid. The gaseous HCl so obtained is a strong acid and ionises almost 100% in water. Fluorine and Chlorine are the most common and most acidic.
Answer:
Atoms of the same element that differ in their numbers of neutrons are called isotopes. Many isotopes occur naturally. Usually one or two isotopes of an element are the most stable and common. Different isotopes of an element generally have the same physical and chemical properties.
Na is a cation (positive) and F is a anion (negative) this is an ionic bond. In a ionic bond the cation loses its valence electrons to give them to the anion. In this case Na will give its valence electron to F so F can complete its octet:)