H pls help 1) If a neutral element has an atomic number of 18 and an atomic mass of 39.95, how many of each subatomic particle does it have?

2) Why are there many, but limited, combinations of elements to make all compounds?

3) Describe the properties of acids and bases. How are salts formed?

4) Explain the differences between mixtures and pure substances.
1) If a neutral element has an atomic number of 18 and an atomic mass of 39.95, how many of each subatomic particle does it have?

2) Why are there many, but limited, combinations of elements to make all compounds?

3) Describe the properties of acids and bases. How are salts formed?

4) Explain the differences between mixtures and pure substances.