Which substance contains only atoms with the same atomic number?

Regents Chemistry Exam August 2024 Question 13

13 Which substance contains only atoms with the same atomic number?

(1) ammonia (3) methane

(2) selenium (4) water

Solution:

Atoms of the same element have the same atomic number. Selenium is the only element listed and can be found on the Periodic Table. Its' name is listed on Table S of the Reference Table. The rest of answer choices are that of compounds. Choice 2 is the correct answer.

LINKS:

Regents Chemistry Guides and Solutions

Chemistry Tutoring

More Regents Chemistry Practice