if all the atoms of an element are identical in various respects then how can two hydrogen atoms combine?

Question

according to the principles of chemical bonding, the electrons must have opposite spins to form a covalent bond.but the electrons of hydrogen are identical.

Answer 1

You can determine the spin of an electron in a single atom only, whether it is similar or opposit, in two different atoms you cannot predict this, because the electron seems clockwise from front will be opposit from behind.Therefore two Hydrogens can be combine,the spin will determine the side of overlapping only.

Answer 2

Identical, except that one is rotated 180 degrees from the other which reverses the spin.
If you rotate a spinning sphere 180 degrees about a line through the equator the direction of the spin will be the opposite. If you and your buddy are looking at either pole of a sphere, and you say it is spinning clockwise, your buddy will say it is spinning counter-clockwise.
Imagine looking at a clock from behind. The '1' is on the left side of the 12 rather than on the right as before. So as the second hand moves from the 12 to the 1, it is moving in the opposite direction.
As an aside, threads are different. Right hand threads remain as such no matter how they are viewed. Spin direction then is then a local property, thread 'orientation' is a global property.