Show that F forms ionic bond with Na but it forms covalent bond with H . (The atomic numbers of H , F and Na are 1 , 9 , and 11 respectively).

An ionic bond is formed between atoms when one atom transfers its electrons from itself to its neighbouring atom. Here, Sodium having one valence electron transfers it to Fluorine atom having seven valence electrons and thus an ionic bond is formed between them whereas HF is a polar covalent compound as Fluorine is more electronegative than hydrogen. Both fluorine and hydrogen are non-metals. Fluorine has seven valence electrons and hydrogen has one valence electron, therefore, they share electrons to form a covalent bond.

Explain why the melting point of sodium chloride is much greater than that of glucose.

Sodium chloride has a high melting point because the lattice is constructed from positive sodium ions and negative chloride ions. This ions attract each other with a strong electrostatic force. To break the bonds between the ions you need high temperature. The intermolecular forces glucose has are hydrogen bonding between the hydrogen and oxygen, dipole dipole between the negative end and positive end of the molecule and London dispersion forces which are weak forces and hence the melting point of sodium chloride is much greater than that of glucose.

Write with an example, how according to Lewis concept, a covalent bond is formed.

The elements share electrons equally in covalent bonding, i.e. both atoms have an equal distribution of electrons in the bond. A covalent bond is formed as a result of the sharing of electrons. The bond is formed by two atomic orbitals overlapping. For the purposes of satisfying the octet rule, each shared electron will be counted towards both atoms' valence shells. Cl 2 has a covalent bond as well. The two chlorine atoms are attracted to the same pair of electrons in the chlorine molecule. In the third energy level, each chlorine atom has seven valence electrons and requires one more electron to form an electron core with an argon electron configuration. The bound pair shared by the two atoms receives one electron from each chlorine atom. Each chlorine atom's remaining six valence electrons are not involved in bonding. Non-bonding electrons, lone pair electrons, and unshared electron pairs are all terms used to describe them.

What type of chemical bond is present in CaO ?

An ionic bond is present in CaO . The atomic number of calcium and oxygen are 2 , 8 , 8 , 2 and 2 , 6 respectively. The two valence electrons of calcium transfer themselves to the oxygen atom. Hence, the Ca 2 + and O 2 - ions are held by a strong electrostatic force forming an ionic bond.