Atom
The smallest unit of matter that has the properties of an element.
Subatomic particle
The particles smaller than atoms, including protons, neutrons, and electrons.
Proton
A subatomic particle with a positive charge found in the nucleus; the number of protons determines the atom’s atomic number
Neutron
A subatomic particle with a neutral charge found in the nucleus, the number of protons + neutrons determines the atom’s atomic mass
Electron
A subatomic particle with a negative charge found outside the nucleus and is responsible for forming chemical bonds
Element
A substance with unique chemical properties made of atoms with the same atomic number; they cannot be broken down by chemical reactions
Electron shell
The region around the nucleus of an atom where the electrons are found.
Atomic nucleus
The center of an atom where the protons and neutrons are found.
Atomic number
The number of protons in the nucleus of an atom.
Atomic mass
The number of protons plus the number of neutrons in the nucleus of an atom.
Isotope
Variants of elements with the same number of protons, but different numbers of neutrons, resulting in different atomic masses
Radioisotope
An unstable isotope that decays into daughter elements by emitting radiation, including subatomic particles.
Half-life
The amount of time it takes for half of a sample of a radioisotope to decay.
Molecule
Two or more atoms held together by chemical bonds, forming the smallest unit of a chemical that takes part in chemical reactions
Chemical Reaction
Occurs when chemical bonds are broken, and elements are rearranged, forming new molecules
Covalent bond
A chemical bond formed by sharing electrons between atoms, forming a molecule.
Non-polar covalent bond
The equal sharing of electrons in a covalent bond
Polar covalent bond
The unequal sharing of electrons in a covalent bond.
Electronegativity
The measure of an atom’s ability to attract electrons toward itself.
Hydrogen Bond
A weak attraction between hydrogen atoms and other electronegative atoms like oxygen or nitrogen, that helps hold certain molecules together, like water or DNA
Hydrophobic
A “fear of water”, hydrophobic molecules do not dissolve in water, like fats or oils
Hydrophilic
A “love of water”, hydrophilic molecules dissolve in water, like sugars and alcohols
Ionic Bond
An electrostatic attraction between oppositely charged ions, forms salts like NaCl (sodium chloride)
Ion
A charged particle (atoms or molecules) that has gained or lost additional electrons.
