If an atom of X reacts with an atom of X what kind of bond forms?
covalent
When an atom of X reacts with another atom of X, it forms a covalent bond.
Covalent bonds are formed when two atoms share electrons in order to achieve a stable electron configuration. In this case, the two atoms of X are bonding by sharing electrons between them. This occurs because both atoms of X have a similar electronegativity, which means they have a similar tendency to attract electrons.
To determine the type of bond that forms between two atoms, you can use the periodic table. Look at the electronegativity values of the elements involved in the bond. If the electronegativity difference is small or negligible (similar electronegativity values), a covalent bond is likely to form. If the electronegativity difference is large, an ionic or polar covalent bond is more likely.
In this case, since the atoms of X are the same element, they have identical electronegativities, leading to the formation of a covalent bond.