A chemical symbol is a notation of one or two letters representing a chemical element. Temporary element symbols are three letters that are based on the element’s atomic number.

Sodium’s Latin name, ‘natrium’, derives from the Greek ‘nítron’ (a name for sodium carbonate). A number of modern languages still call the element natrium instead of sodium, and it’s this name that its chemical symbol, Na, comes from.

Molybdenum

Pb

It is a very pale blue color easy to see with your naked eyes. This is very similar to the fact that you can see water inside a glass of water, but if you let the water get warm and evaporate into the air you cannot see it any more even though it is still there in the room with you!

Oxygen molecule is 2 oxygen atoms in a covalent bond, whereas an oxygen atom is an atom with 8 electrons (6 valence electrons). Thus, clearly, any element in a bonded state is always more stable than when in an un-bonded state.

As bond order of nitrogen is more than that of oxygen, nitrogen is more stable than oxygen. According to Molecular orbital theory, N2 has 3 bond orders whereas O2 has 2. Higher the bond order, more will be the overlapping of atoms, thus more will be stability. So, N2 is more stable than O2.

This is because according to molecular orbital theory it has same no . of antibonding and bonding molecules. So between its two atoms bond order is zero that means there is no existence of Ne2 molecule.

according to molecular orbital theory(MOT) the bond oder is 0 for H2(2-) molecule. like He atom. when bond order is 0 that mean no bond is formed there. that why H2(2-) does not exist.

There is no bond existing between atoms of He2​. So He2​ does not exist.

Neon molecule does not exists because it has no bond order and cannot exist. Neon is denoted by Ne which is noble gas. Noble gases are non-reactive by nature. This is why it does not need to react with any other atom and so has no bond order and cannot exist.