Properties of covalent compounds Covalent compounds generally have much lower melting and boiling points. Covalent compounds do not pass electric current when melted. They are generally liquids or gases at room temperature. Covalent compounds are not soluble in water. They are not made up of ions, they are made of molecules. Metallic Bonding Metal atoms lose electrons from the outermost shell and become positive ions. Most atoms lose electrons. Electrons are always moving. Many such positing ions from layers. Electrons present in the structure. The positive ions and electrons attract in a metallic structure. This attraction between positive metal ions and the electrons sea is called metallic bonding. They lose electrons, and become positive ions. Why are metals ductile and malleable, Metal atom storm layers in the metallic structure. These layers of atom slide one over the other when a force is applied. Why are metals good conductors of electric current? There are so many electrons, and the free moving electrons can carry the current. Why metals have high melting and boiling pints: Metal atoms are closely packed in the metallic structure. SO metals have high density in nature. Strong attracting between free negative electrons and metallic ions in the structure makes the boiling and melting points high. Structure of substances: Simple molecular structure - molecules formed from covalent bonding are not attracted each other much. Giant covalent Structure: Three examples you need to learn - Diamond, Graphite (giant atomic) and Silicon dioxide (sand) (SiO2) (Giant molecular) Diamond and graphite are pure crystal (Definite shape & structure) form of Carbon.