— Physical Chemistry Chemistry Question

Hydrogen is the most abundant element at the core of the sun.

Hydrogen is the only element in the periodic table that can exist without a neutron. This suggests that a neutron is essential for binding positively charged protons in the nucleus.

The number of neutrons for heavy nuclei exceeds the number of protons, because the electrostatic repulsion between protons is long–range whereas the strong nuclear force among the protons and the neutrons is short–range.

Helium is the second–most abundant element in the universe. The molar ratio between hydrogen nuclei (proton) and helium nuclei (α–particle) is about 3 to 1.

Helium was first made in the interior of the first star in the history of the universe.

The mass of an α–particle = 2 × (proton mass + neutron mass).

Neutral atoms were first made before the birth of the first star in the history of the universe.

The discovery of argon precedes the discovery of the octet rule.

Mendeleev's periodic table precedes the discovery of argon.

The discovery of proton precedes the discovery of electron.

The ionization energy of hydrogen is greater than the bond energy of the hydrogen molecule.

The enthalpy of formation of CO₂(g) is about the same as twice the enthalpy of formation of H₂O(g), because there are two electronegative oxygen atoms in CO₂ whereas there is only one in H₂O.