Chapter 2 Flashcards
matter
anything that takes up space and has mass
element
substance that can not be broken down to other substances by chemical reactions
compound
substance that consists of two or more different elements combined in a fixed ratio
essential elements
of 92 natural elements, only 20-25% are needed for an organism to live a healthy life and reproduce
Trace elements
required by organism only in minute quantites
atom
smallest unit of matter that still retains the properties of an element
atomic nucleus
protons and neutrons packed together in a dense core
dalton
unit of measurement for atoms
atomic number
number of protons which is unique to the element is written to the left of the symbol
mass number
sum of protons plus neutrons in nucleus of an atom
number of neutrons
mass number- atomic number
atomic mass
the mass number is an approximation of the total mass of an atom
isotopes
different number of neutrons for same element
radioactive isotope
the nucleus decays spontaneously, giving off particles and energy
what happens when the atom decays?
the atom turns into a new atom of a different element
what are radioactive isotopes used for?
to follow atoms through metabolism, the chemical processes of an organism
energy
the capacity to cause change
potential energy
energy that matter possesses because of its location or structure
electron shells
where electrons are found each with a characteristic average distance and energy level
valence electrons
outer electrons
valence shell
outermost electron shell
chemical bonds
transfer of valence electrons
covalent bond
sharing of a pair of valence electrons by two atoms
molecule
two or more atoms held together by covalent bonds
