Answer : The properties which would be the same among isotopes of the same element are Flammability and Color
Explanation :
Isotopes are the elements that have same number of electrons and protons but they differ in number of neutrons.
The chemical properties of an element are determined by its valence electrons and since isotope have same number of electrons, they have similar chemical properties.
But isotopes have different number of neutrons. Neutrons are the subatomic particles which are present in the nucleus. They are charge less particles and they have mass. Therefore when the elements have different number of neutrons, their atomic masses differ.
As a result, isotopes have different mass related physical properties.
Let us discuss the given properties now
1) Flammability : Flammability in simple words means the ability of the substance to catch fire or the ability to burn. This is mainly dependent on the reactivity which is in turn dependent on the number of electrons.
Since the isotopes have same number of electrons, they show similar flammability.
2) Density : Density is defined as mass per unit volume. This property involves mass and we know that isotopes have different masses. Therefore they have different densities too.
3) Melting point : Melting point is a physical property which is mainly dependent on the molecular weight of the substance. Since isotopes have different masses, they tend to show different melting points.
4) Color : The color of the element is mainly dependent on the arrangement of electrons around the nucleus. Isotopes have same number of electrons which means the arrangement would also be the same. Therefore the isotopes of the same element do not show different colors.
The properties which would be same among isotopes of the same element are
1) Flammability
4) Color
which is called the Avogadro’s number.