How do the nuclei of different isotopes of an element vary?

isotopes of an element have nuclei with the same number of protons, but a different number of neutrons.
isotopes of an element have nuclei with the same number of protons and the same number of neutrons.
isotopes of an element have nuclei with a different number of protons, but the same number of neutrons.
isotopes of an element have nuclei with a different number of protons, but the same number of electrons.

isotopes of an element has same number of proton but different number of neutron.

Explanation:

Isotope: The atoms of element having same atomic number but different mass number are called isotope.

Hydrogen has three isotopes called as

1.protium

2.duetrium

3.tritium

All of the isotopes of hydrogen have same atomic number but different masses 1,2,3 respectively.

Isotopes have same outermost shells there for having same chemical properties.

Isotopes have different nuclie due which they have different physical properties.

Tritium the 3rd isotop having diffrent prton to neutron ration emitts radiation there it in traces.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.