Question

the elements in group 17 of the periodic table are all called halogens. all halogens have the same
atomic number.
atomic mass.
number of possible isotopes.
number of valence electrons.

Explanation:

• Atomic number: Each element has a unique atomic number, so halogens (different elements) can't have the same atomic number.
• Atomic mass: Halogens are different elements (e.g., F, Cl, Br) with different atomic masses.
• Number of possible isotopes: Different halogens have different numbers of isotopes (e.g., Cl has 2 main isotopes, F has 1 stable isotope).
• Number of valence electrons: Elements in the same group have the same number of valence electrons. Group 17 elements have 7 valence electrons, so all halogens (group 17) have 7 valence electrons.

Answer:

D. number of valence electrons