Question

which is a physical property used to distinguish metals from other elements?
luster
conductivity
density
reactivity
12 multiple choice 1 point
two scientists, ____ and ____ developed the first classifications of elements that we now know as the periodic table.
bohr; mendeleev
meyer; bohr
planck; einstein
mendeleev; meyer
13 multiple choice 1 point
effective nuclear charge ($z_{\text{eff}}$) was derived from...
coulomb’s law.
newton’s first law of thermodynamics.
the photoelectric effect.
the theory of relativity.

Explanation:

Question 1 (Physical Property to Distinguish Metals)

To determine the physical property distinguishing metals:

• Luster: Some non - metals (e.g., graphite) can have luster, so not unique.
• Conductivity: Metals are good electrical conductors, while non - metals (except graphite) and metalloids have lower conductivity. This is a key physical property for distinction.
• Density: There are non - metals with high density (e.g., iodine) and metals with low density (e.g., lithium), so not a reliable distinguisher.
• Reactivity: Reactivity is a chemical property (involves chemical reactions), not physical.

So conductivity is the best choice.

• Bohr: Known for Bohr model of atom, not periodic table.
• Mendeleev: A key scientist in developing the periodic table.
• Meyer: Also worked on classifying elements for the periodic table, independent of Mendeleev.
• Planck: Known for quantum theory, not periodic table.
• Einstein: Known for relativity, not periodic table.

So Mendeleev and Meyer developed the first classifications for the periodic table.

• Coulomb’s Law: Deals with electrostatic forces between charged particles. Effective nuclear charge ($Z_{eff}$) relates to the attractive force between the nucleus and electrons, so it is derived from Coulomb’s Law.
• Newton’s First Law of Thermodynamics: Newton's laws are about motion, and thermodynamics has its own laws (this option is incorrect as a combination).
• Photoelectric effect: Related to photon - electron interactions, not $Z_{eff}$.
• Theory of relativity: Deals with space - time and high - speed/mass - energy, not $Z_{eff}$.

So $Z_{eff}$ is derived from Coulomb’s Law.

Answer:

conductivity (the option with "conductivity" as its text)

Question 12 (Scientists Who Developed Periodic Table Classifications)