Defining the Atom

Front

Atom Noun

---

[at-uhm]

Back

Atom

---

The smallest particle of an element that retains all the chemical properties of that specific element.

---

Example: This diagram shows an atom's structure: a central nucleus containing protons and neutrons, with electrons orbiting the nucleus in distinct energy shells.

Front

Subatomic particle Noun

---

[suhb-uh-tom-ik par-ti-kuhl]

Back

Subatomic particle

---

A particle smaller than an atom, such as a proton, neutron, or electron, which are the constituents of atoms.

---

Example: This diagram shows the three main subatomic particles—protons (green) and neutrons (blue) in the nucleus, and electrons (red) orbiting the nucleus.

Front

Electron Noun

---

[ih-lek-tron]

Back

Electron

---

A stable, negatively charged subatomic particle that orbits the nucleus of an atom in the space surrounding it.

---

Example: This diagram shows that an electron is a negatively charged particle that orbits the central nucleus of an atom, which contains protons and neutrons.

Front

Proton Noun

---

[proh-ton]

Back

Proton

---

A stable, positively charged subatomic particle found within the atomic nucleus, with a mass similar to a neutron.

---

Example: This diagram shows a proton (red sphere) located inside the atom's central nucleus, along with a neutron, defining its place within the atom.

Front

Neutron Noun

---

[noo-tron]

Back

Neutron

---

A subatomic particle with no electric charge, found in the atomic nucleus and having a mass similar to a proton.

---

Example: This diagram shows a neutron (blue sphere) as a particle with no charge, located inside the atom's central nucleus along with protons.

Front

Nucleus Noun

---

[noo-klee-uhs]

Back

Nucleus

---

The very dense, positively charged central region of an atom, composed of protons and neutrons, containing most of its mass.

---

Example: This diagram shows an atom's central core, the nucleus, which contains positively charged protons and neutral neutrons, with electrons orbiting around it.

Front

Cathode-ray tube Noun

---

[kath-ohd-rey toob]

Back

Cathode-ray tube

---

A vacuum tube containing electrodes, used in experiments to discover electrons by observing beams of particles.

---

Example: This diagram shows a cathode-ray tube, where a heated cathode emits an electron beam that travels to a fluorescent screen, causing it to glow.

Front

Cathode Noun

---

[kath-ohd]

Back

Cathode

---

The negatively charged electrode in an electrochemical cell or vacuum tube from which electrons are emitted.

---

Example: This diagram shows a cathode ray tube. The cathode, the negative (-) terminal, emits a beam of invisible rays (electrons) that travel towards the positive (+) anode.

Front

Anode Noun

---

[an-ohd]

Back

Anode

---

The positively charged electrode in an electrochemical cell or vacuum tube that attracts negatively charged particles like electrons.

---

Example: This diagram shows an anode as the negative terminal in a battery, where it releases electrons that flow through a circuit to power a lightbulb.

Front

Cathode ray Noun

---

[kath-ohd rey]

Back

Cathode ray

---

A stream of high-velocity electrons that are produced in a vacuum tube when a voltage is applied across electrodes.

---

Example: In a special glass tube with low-pressure air, high voltage creates a beam of particles called a cathode ray, which travels from the negative cathode to the positive anode.