• N₂ has a σ-bond and a δ-bond. First the two p_z-orbitals overlapped, as they collide with each other, to form the σ-bond. Then the two sets of the other p-orbitals overlapped, folding towards each other to form the δ-bond.
• O₂ has a σ-bond and a π-bond.
• Phosphorus is below nitrogen in the Periodic Table, we would expect P₂ to have a σ-bond and a δ-bond.
• Sulphur is below oxygen in the Periodic Table, we would expect S₂ to have a σ-bond and a π-bond .
• Chlorine has a σ-bond, just like fluorine.

Water is a compound (or molecule) made from hydrogen and oxygen. Mixture is very different from molecules. If I mixed two molecules of hydrogen gas and one molecule of oxygen gas in a plastic bag. I will not see water. I see nothing because they are still oxygen and hydrogen gas. The two must react to give water. So water is not oxygen and hydrogen, but made from oxygen and hydrogen having its own properties very different from hydrogen and oxygen. If in a beaker of water there is no other foreign matter (meaning other stuff) then that water is pure.

The second ionization potential is defined as the energy used to remove an electron from a gaseous single positively charged atom to give a gaseous ion and a gaseous electron. Example.

Elements on the left hand side of the Periodic Table like to give off their valence electrons and that on the right hand side like to take in valence electrons - to form a valence shell of eight electrons. The "Octet Rule".

For the elements on the left hand side those at the bottom will give off its valence electrons most readily since the valence electrons are now shielded from the positive nucleus by the inner shells of electrons. For a similar reason those at the top right hand corner attract valence electrons more easily since the positive nucleus is less shielded as there is less shell of electrons.

Polar means having two poles and it should behave like a magnet. Molecule means a group of atoms bonded together. So this group of atoms held together must have a positive pole and a negative pole to behave like a magnet.

Now there is a concept known as electronegativity - the different abilities of atoms to hold tightly to its valence electrons. Let us consider a carbon-fluorine σ-bond. Carbon wants to keep its electron and fluorine wants to take it. So they agreed to share with each contributing one electron to form a covalent bond. Like all agreements carbon must read the fine prints. In a covalent bond the electrons are suppose to move around the two atom centers and thus hold the atoms to each other. That is on average each atom must have an equal share of the electrons in the bond. However because of the difference in electronegativity the electron spend more time with fluorine than carbon. So on average carbon experience a lost of electron and fluorine a gain of electrons. Thus the carbon-fluorine covalent bond actually has a slight positive charge at the carbon center and a slight negative charge at the fluorine center.

But the bond is only part of a molecule. In a molecule like carbon dioxide, O=C=O, you have two negative ends and a positive carbon at the center. This molecule cannot behave like a magnet. So the geometry of the molecule is important. Similar carbon tetrafluoride has a tetrahedral structure so is like a ball with carbon at the center, so it is also not polar.

Methylfluoride, CH₃F, also has a tetrahedral structure but the surface where fluorine is will be slightly negative, while the other hemisphere is slightly positive. So it is a polar molecule.

In conclusion you need to focus on two concepts.

Boric acid: 5.07   Carbonic acid: 3.68   Lactic acid: 2.43   Phenolic acid: 9.89

When an acid anhydride (HA) is added to water it dissociates to give the hydronium ion.