Covalent compounds are formed when two non-metal atoms share electrons to attain a stable octet configuration. In contrast, ionic compounds are formed when a metal and a non-metal bond through transfer of electrons.

Heading: Factors affecting the tendency to form covalent compounds

- Electronegativity: The tendency to form covalent compounds increases with increasing electronegativity difference between atoms. This is because a large electronegativity difference leads to a stronger attraction between the positively charged nucleus of one atom and the negatively charged electrons of the other, which favors transfer of electrons and formation of an ionic bond.
- Size of atoms: The tendency to form covalent compounds increases with increasing size of atoms. This is because larger atoms have more electrons and a weaker attraction between the nucleus and outermost electrons, which favors sharing of electrons and formation of a covalent bond.
- Ionization energy: The tendency to form covalent compounds increases with decreasing ionization energy of the atoms. This is because low ionization energy means that the atom has a weak hold on its electrons, making it easier for them to be shared with another atom to form a covalent bond.

Heading: Factors affecting the tendency of Mg to form covalent compounds

- Electronegativity: Magnesium (Mg) has an electronegativity of 1.31, which is higher than some other metals like sodium (Na) but still lower than most non-metals. Therefore, Mg has a moderate tendency to form covalent compounds with non-metals like carbon or oxygen.
- Size of atoms: Mg has a small atomic radius compared to many non-metals, which means that it has a relatively strong attraction between its nucleus and outermost electrons. However, this does not completely rule out the possibility of covalent bonding, especially with non-metals that have similar atomic radii like carbon or nitrogen.
- Ionization energy: Mg has a relatively high ionization energy compared to non-metals, which means that it has a strong hold on its electrons. However, this does not completely rule out the possibility of covalent bonding, especially with non-metals that have similar ionization energies like boron or carbon.

Overall, Mg has a moderate tendency to form covalent compounds depending on the electronegativity and size of the non-metal it is bonding with, as well as the ionization energy of Mg itself.