Essential Question: what makes up an atom? The Atom Essential Question: what makes up an atom?

What is an “atom”? Nearly everything is made up of atoms. Atoms are the building blocks of matter. Matter is anything that has mass and takes up space. Atoms are the smallest particle into which an element can be divided and still be the same substance. An element is one or more of the same kind of atom chemically combined. Oxygen, for example, is an element.

What are atoms made of? Atoms are made of even smaller particles called subatomic particles. Point of confusion: “I thought atoms were the smallest particles? How can they be made up of “even smaller” particles? If we look back at the definition, atoms are the smallest particle of an element that still maintains the same properties of that element. In other words, if we divide up an atom into its smaller pieces, it no longer maintains all the properties of the element. Therefore, those even smaller particles are not “building blocks” of matter, because unless they are combined to form an atom, they do not look like or act like any of the elements.

What are atoms made of? Atoms are made of even smaller particles called subatomic particles. The three subatomic particles are called protons, neutrons, and electrons. Proton and neutrons exist together in the nucleus, or center of the atom. Electrons exist in the area surrounding the nucleus called the “electron cloud.”

Neutrons Located in the nucleus Do not have an electrical charge

Protons Located in the nucleus Have a positive (+) electrical charge

Electrons Located outside the nucleus, in the electron cloud Have a negative (-) electrical charge

What do atoms look like? You’ve probably seen depictions of atoms before, like these: In truth, our idea of what an atom looks like has changed greatly over the years since their discovery.

What do atoms look like? Bohr’s Model Electrons in the cloud float around in circles, called orbits or shells. Each of these electron shells can hold a certain number of electrons Electrons in the outermost shell or “valence electrons” combine with other atoms to form compounds and molecules.

Now You Try! Complete the What Makes Up an Atom Worksheet. Once you are done with that worksheet, you are done for today!

How do I know how many protons, neutrons, and electrons an atom has? Atoms have an equal number of protons and electrons. The atomic number (top number) on a Periodic Table Square tells you the number of electrons (and protons). The atomic mass (bottom number) tells you the neutrons with a simple math problem. Atomic mass – atomic number = number of neutrons

How do I know how many protons, neutrons, and electrons an atom has? Copy the periodic table square into your notebook. Atomic number (number of protons or electrons) Chemical symbol (1-2 letters) Element name Atomic mass (atomic mass – atomic number = number of neutrons)

How are the elements on the Periodic Table arranged? Arranged by how metallic they are (blue is metal, orange is metalloid, and green is nonmetal) Rows are called “periods” Columns are called “groups”

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