Chemistry Pre-Ap Biology Study

Matter

Anything that takes up space and has mass.

Element

Substance that cannot be broken down to other substances through chemical reactions. Each has a symbol. 92 occurring in nature.

Compound

Substance consisting of two or more different elements combined in a fixed ratio.

*Characteristics different than those of its elements

Atom

Smallest unit of matter that retains the properties of an element. Composed of subatomic particles. Mostly empty space.

Subatomic particles

Neutrons, protons, electrons. Make up atoms.

Proton

One unit of positive charge. Approximately one dalton. Located in nucleus.

Electron

One unit of negative charge. Located outside of nucleus.

Atomic Nucleus

Dense core packed with protons and neutrons.

Neutrons

Electrically neutral. Approximately one dalton.

Atomic Number

The number of protons (which is unique to that element) and written as a subscript to left of element symbol. Also tells us number of electrons since P=E if atom is neutral

Mass Number

Sum of the protons and the neutrons. An approximation of the atomic mass.

Isotopes

Same number of protons, but different number of neutrons and therefore different mass. Same element.

Potential Energy

Energy matter possesses because of its location or structure. Electrons have this based on distance from nucleus.

Electron Shells

Where electrons are found, each with characteristic average distance and energy level. Electrons can change these by absorbing or losing energy.

Valence Electrons

Electrons in the outermost shell.

Covalent Bond

Sharing of a pair of valence electrons by two atoms.

Molecule

Two or more atoms held together by covalent bonds.

Single Bond

One pair of shared electrons.

Structural Formula

H--H. Notation which represents both atoms and bonding.

Double Bond

Sharing two pairs of valence electrons.

Valence

Bonding capacity. Equal to the number of unpaired electrons required to complete the outermost (valence) shell.

Electronegativity

The attraction of a particular kind of atom for the electrons of a covalent bond.

Nonpolar Covalent Bond

Covalent bond in which electrons are shared equally.

Polar Covalent Bond

Where one atom is bonded to a more electronegative atom and the electrons of the bond are not shared equally.

Ionic Bonds

The attraction of cations and anions. The transfer of electrons creates ions which form an ionic bond.

Ion

A charged atom.

Cation

A positively charged atom.

Anion

A negatively charged atom.

Ionic Compounds

Or Salts. Compounds formed by ionic bonds.

Hydrogen Bond

When a hydrogen atom covalently bonded to an electronegative atom is also attracted to another electronegative atom.

van der Waals Interactions

Ever changing regions of positive and negative charge that enable all atoms and molecules to stick to one another.