When H is positive and S is negative
The structure of Methanol (CH₃OH) is shown below. This structure contains
2 lone pair of electrons on oxygen (highlighted red). Electronic configuration of oxygen is,
Oxygen = 8 = 1s², 2s², 2px², 2py¹, 2pz¹
There are six electrons in valence shell of oxygen, among these six electrons two electrons are unpaired and involved in forming covalent bond with hydrogen and carbon, while remaining 4 electrons in pair (i.e. 2s², 2px²) exists as lone pairs.
A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction.