In modern periodic table while going from top to bottom in a group ______.

 

Here all the given options are Exothermic reactions. Exothermic reactions are those reactions which involves the release of heat.

Generally all the combining reactions are exothermic in nature.

Covalent bonds are bonds formed between two non metals by sharing of electrons in their outer most orbits for stable.

Atoms of the same element can have same atomic number and number of electrons since, the atomic number is the number of protons and the number of protons and eectrons are the same in an element.

Hence, the atoms of the same element may differ in their atomic mass since it depends on the number of neutrons it holds and such atoms are called isotopes.

Molecular compounds are those with covalent bonds between the elements and those elements are typically non metals.

Here in the given options, Ar is an element. NaI has an ionic bond. Hence, N2O4 has a covalent bond between the two non metals and is a molecular compound.

All atoms of an element have the same number of protons. The number of protons in an element is a primary identifier known as its atomic number. The number of electrons is the same as the number of protons.

An ionic bond is formed in between the two atoms with the transfer of electrons from an atom to the other to become stable after pairing.

The atom which has low ionization energy will give some of its electrons to get stable electronic configuration .