Chemical Elements & Compounds

Vocabulary flashcards covering basic chemical concepts including matter, atomic structure, isotopes, ions, and chemical bonding types.

Matter

Anything that has weight (gravity) and takes up space; all living organisms are composed of it.

Element

A substance that cannot be broken down into another substance by ordinary chemical reactions.

Atom

The smallest unit of matter that still retains the properties of that element.

Protons

Subatomic particles located in the nucleus with one unit of positive charge and a mass of $1.7 \times 10^{-24}$g ($1$Dalton).

Neutrons

Neutral subatomic particles located in the nucleus with a mass very close to that of a proton ($1$Dalton).

Electrons

Subatomic particles located outside the nucleus in orbitals with one unit of negative charge and a mass that is $1/2000$ that of a proton.

Atomic Number

The number of protons that an element contains.

Atomic Weight (Mass Number)

The sum of the number of protons and the number of neutrons in the nucleus of an atom.

Isotopes

Atoms of an element that have a different number of neutrons.

Radioactive

A property of unstable isotopes, such as Carbon-14, that emit nuclear particles and energy from their nuclei.

Ions

Atoms of an element that have gained or lost an electron, resulting in a charge.

Anion

A negatively charged ion that has gained an electron and is attracted to a positively charged electrode (anode).

Cation

A positively charged ion that has lost an electron.

Compounds

Substances that are composed of two or more elements in fixed ratios, such as $NaCl$ or $H_2O$.

Chemical Bonds

Electronic forces that hold atoms together in compounds and molecules, formed when the electrons of each atom interact.

Potential Energy

Stored energy possessed by electrons because of their position or location within the atom.

Kinetic Energy

The energy of motion possessed by electrons because they are constantly in motion.

Electron Orbitals

The three-dimensional space around the nucleus of an atom where an electron is found $90\%$ of the time; each can hold a maximum of $2$ electrons.

Valence Shell

The outermost electron shell of an atom.

Valence Electrons

Electrons in the outermost shell that react to form compounds.

Chemically Inert

The state of elements like Helium, Neon, and Argon that have filled outer shells and are unreactive.

2-8-8 Rule

The guideline for electronic configuration where the first shell holds up to $2$ electrons, and the second and third shells hold up to $8$ electrons each.

Covalent Bonds

Strong chemical bonds that occur when atoms share pairs of electrons to complete their valence shells.

Non-Polar Covalent Bonds

Bonds where atoms share pairs of electrons equally, with electrons spending equal time in each atom's orbital.

Polar Covalent Bonds

Bonds where electrons are shared unequally because one atom is more electronegative, resulting in a molecule with charged parts.

Electronegativity

A term used to describe how strongly an atom attracts electrons.

Hydrogen Bonds

Weak secondary bonds that form between polar molecules or between polar molecules and ions; essential for holding DNA and proteins together.

Ionic Bonds

Chemical bonds that occur between oppositely charged ions.