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S8P1.a
| Term | Definition |
|---|---|
| Atom | the smallest unit of an atom expressed in atomic mass unit. |
| Element | a substance that cannot be separated or broken down into simpler substances by chemical means. |
| Nucleus | in physical science an atom's center region which is made up of protons and neutrons. |
| Proton | a substance particle that has a positive charge and that is found in the nucleus of an atom. |
| Neutron | a substance particle that has no charge and that is found in the nucleus of an atom. |
| Electron | a substance particle that has a negative charge. |
| Atomic Number | the number of protons in the nucleus of an atom ;the number is the same for all atoms of an element. |
| Atomic Mass | the mass of an atom expressed in atomic mass units. |
| Pure Substance | a sample of matter, either a single element or a single compound that has definite chemical and physical properties. |
| Chemical Symbol | a one or two letter code that represents an element. |