1Four molecular models are shown: H₂, H₂O, O₂ and NaCl. Which substances do they represent?
2What is the difference between the molecular models of H₂ and H₂O?
3What is the difference between the molecular models of O₂ and NaCl?
4Water has the formula H₂O and salt has the formula NaCl. How are the elements held together in millions of compounds like these?
5What is a chemical bond? Give an example.
6Why do inert gases not take part in chemical reactions while other elements do?
7What is an electrovalent bond, and between what kinds of elements does it form?
8Explain the formation of sodium chloride (NaCl), with electron configurations and equations.
9How is magnesium oxide (MgO) formed? Write the equations.
10Why is the formula of calcium chloride CaCl₂ and not CaCl?
11Write any three characteristics of electrovalent compounds.
12Why does a sodium atom become a positive ion when it loses an electron?