Elements are one type of pure substance. In an element, every atom is the same as every other atom. It
has the same properties throughout. All of the known elements on Earth are arranged in the periodic
table in order of atomic number. That's the number of protons its atoms have. Hydrogen is an element
with atomic number 2, oxygen is atomic number 8 and chlorine is 17. Each element has a symbol on the
periodic table. Hydrogen is H, oxygen is O and chlorine is Cl. Because every atom of an element is the
same, you cannot break an element down into any smaller unit of matter.
Which of the following best describes the relationship between oxygen and chlorine?
A. Oxygen and chlorine have the same
B. Oxygen atoms have fewer protons than
symbols.
chlorine atoms.
C. Oxygen and chlorine have the same
D. Oxygen atoms have twice as many protons
properties.
as chlorine atoms.