A Tiny World of Building Blocks

On a rainy afternoon, Sofia and Brianna visited a science center. A display showed a magnified model of an atom. “Everything around us is made of tiny particles called atoms,” their guide explained. “Atoms are far too small to see with our eyes.” The model showed a compact center, called the nucleus, containing protons and neutrons. Electrons occupy regions around the nucleus. The guide pointed out that most of an atom’s volume is empty space, even though objects made of atoms can feel firm when we touch them. At another station, Sofia arranged two white hydrogen pieces and one red oxygen piece. Together they represented a water molecule. Atoms joined by chemical bonds make molecules, the guide said. A molecule’s formula tells which kinds of atoms it contains and how many of each. In H₂O, the small 2 means there are two hydrogen atoms; the O has no number, so there is one oxygen atom. Brianna noticed that the display included many different kinds of atoms. Each kind is an element. Elements can join in different combinations, making many substances. The guide added that scientists have identified 118 elements. As they left, Sofia and Brianna looked at the raindrops on the window and imagined the tiny particles that make up the water.

Reading Comprehension

Think About the Science