Boron is indeed a very hard substance, which does indicate high lattice energy. This is because the lattice energy is a measure of strength of the forces between the ions in an ionic solid; greater the lattice energy, stronger the forces which result in harder and more stable compound. This makes Statement I true. Statement II is also true. Boron, is the first member of group 13 elements, it has highest melting and boiling points among its group members (AI, Ga, In, Tl). This can be attributed to the strong covalent bonding in boron due to its small size, which requires a high amount of energy to breaks. Therefore, both Statement I and Statement II are true.