> See also: > - [[The Periodic Table]] > - [[Molecules]] # Atoms and Elements > [!quote] Summarizing Scientific Knowledge in a Single Sentence > "All things are made of atoms - little particles that move aroudn in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into another." > - Richard P. Feynman An **atom** is the smallest particle of an element that has the properties of an [[The Periodic Table|element]] and can be part of chemical compounds A molecule is a combination (bond) of 2 or more atoms. [[Molecules]] can be composed of a single element species while **compounds** are always composed of different elements. An **atomic element** is an element exactly as it appears on the periodic table ## Structure of Atoms There are three main particles that make up atoms: 1. **Neutrons** (Neutral) 2. **Protons** (Positively Charged) 3. [[Electrons]] (Negatively Charged) ## Atomic Properties **Atomic Number:** the total number of *protons* in a nucleus - Is unique for each element - Defines an element's identify **Mass Number:** the sum of the protons and neutrons within a nucleus - aa - a - as - A molecule is made up of multiple atoms (either identical or unique) A compound is a type of molecule that contains at least two unique atoms > The confusing thing is that molecules with a single element ![[Pasted image 20220710210550.png|500]] # Molecules vs Compounds > All compounds are molecules, but not all molecules are compounds. ### Molecular (Covalent) Compounds --- ### Ionic Molecules > In ordinary chemical reactions, the nucleus of each atom (and thus the identity of each element) remains unchanged. Electrons, however, can be: - Added to atoms by transfer from other atoms. (Ionic) - Lost by transfer to other atoms. (Ionic) - Shared with other atoms. (Covalent) ### Predicting Ionic Charge - Metals tend to make positive charges - Nonmetals tend to make negative charges - [ ] Predict the type of compound formed from elements based on their locations within the periodic table.