We once thought that atoms are indivisible, but we now know that they are made of three subatomic particles: the proton, the neutron, and the electron. This activity helps to reinforce the location, mass, and charge of these particles and the meaning of two key vocabulary terms: atomic number and mass number. Students will identify each part of an atom and describe how to find their atomic and mass numbers.
The proton and neutron are found in the nucleus of the atom. The proton has a relative mass of 1 amu and a relative charge of +1. The neutron has a relative mass of 1 amu and a neutral charge. Most of the mass of the atom is found in the small, dense nucleus because these two particles are the more massive of the three.
The electron, by comparison, has a mass almost 2000 times less than a proton or neutron. That means that it would take around 2000 electrons to equal the mass of one proton. Because the biggest atoms we know of have only 118 electrons, the electron contributes almost nothing to the atom in terms of mass. Each does, however, have a relative charge of -1.
The atomic number is defined as the number of protons in an atom. Because atoms are electrically neutral, the atomic number also tells us how many electrons are in a neutral atom.
The mass number is simply the mass of the atom. Since the protons and neutrons contribute the mass to the atom, the mass number tells us the number of protons and neutrons combined.
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Student Instructions
Create an atom diagram and explain the parts of an atom, focusing in on their atomic number, mass, and charge.
Engage students by letting them build a physical atom model using common supplies like colored beads, pipe cleaners, and paper plates. This brings abstract concepts to life and helps reinforce the parts of an atom in a fun, memorable way.
Collect items such as paper plates (nucleus base), colored beads or pom-poms (protons, neutrons, electrons), pipe cleaners or string (electron paths), and markers for labeling. These affordable supplies make the activity accessible for every classroom.
Choose a distinct color for each particle type (e.g., red for protons, blue for neutrons, yellow for electrons). This visual distinction helps students remember the differences and supports visual learners.
Ask students to glue or tape protons and neutrons in the center of the plate to form the nucleus. Then, attach electrons to pipe cleaners or string and arrange them as orbits around the nucleus, showing how electrons move in different energy levels.
Have students use markers or sticky notes to label protons, neutrons, electrons, atomic number, and mass number on their models. This reinforces key terms and helps students connect visuals with vocabulary.
An atom is made of three main parts: protons (positive charge), neutrons (no charge), and electrons (negative charge). Protons and neutrons are found in the nucleus, while electrons orbit around the nucleus.
The atomic number equals the number of protons in an atom. The mass number is the sum of protons and neutrons. Both numbers help identify and describe different elements.
Electrons have a mass nearly 2000 times less than a proton or neutron. This means their contribution to an atom’s total mass is almost negligible, so most of the atom’s mass comes from protons and neutrons in the nucleus.
The atomic number is the total number of protons in an atom, which defines the element. The mass number is the combined total of protons and neutrons, showing the atom’s total mass.
Remember that protons and neutrons are in the nucleus (center), while electrons move around the nucleus in energy levels or shells. A diagram or model can help reinforce these locations visually.