what particles are free to drift in metals?

cations, electrons, neutrons, or protons?

and what is the SI unit of mass? is it kilogram

kg is correct for the SI unit of mass. Electrons conduct electricity; therefore, the electrons must be free to move in metals.

cations

In metals, the particles that are free to drift are electrons.

To determine which particles are free to drift in metals, we need to consider the atomic structure of metals. Metals are composed of positive cations, usually metal ions, surrounded by a sea of delocalized electrons. The positive cations (protons) are held in a fixed position within the lattice structure of the metal and are not free to move. Similarly, neutrons are neutral particles and do not contribute to the flow of charge within a metal.

Therefore, the correct answer is electrons. Electrons are free to move within metals and are responsible for the conductivity of electricity in these materials. This movement of electrons is referred to as electron flow or electron drift.

Regarding the second question, the SI (International System of Units) unit of mass is indeed the kilogram (kg). The kilogram is the base unit for mass in the SI system and is defined as the mass of the International Prototype of the Kilogram, a platinum-iridium cylinder kept at the International Bureau of Weights and Measures in France.

Which of the following are free to drift in metals?

a. neutrons

b. electrons

c. pions

d. cations

e. protons