AP Bio Key terms Chapter 2

Matter

Anything that takes up mass and space

Element

a pure substance made entirely of one type of atom

Atom

the basic building block of all matter

Proton

a tiny, positively charged particle found inside the center (nucleus) of every atom

Neutron

a tiny, subatomic particle found in the center (nucleus) of almost every atom

Electron

a fundamental subatomic particle with a negative electric charge

Nucleus

The "control center" of a cell that stores DNA and directs all of the cell's activities.

Isotope

different versions of the same chemical element

Radioisotope

an unstable version of a chemical element

Half-life

the exact amount of time it takes for half of a specific substance to break down, decay, or disappear

Electron shell

an orbit or energy level that electrons occupy as they circle the center of an atom

Valence shell

the very outermost ring or layer of electrons surrounding an atom's nucleus

Orbital

a 3D region of space around an atom’s nucleus where an electron is most likely to be found

Electronegativity

an atom's ability to attract shared electrons towards itself in a chemical bond

Van der waals interaction

the weak, temporary attractions between neutral atoms or molecules that are very close together