Chapter 2 Flashcards
electrons
negligible mass; negative charge
protons
have mass; positive charge
neutrons
have mass; no charge
1 dalton
1.7x10^-24
element
a fundamental substance containing only one kind of atom
atomic number
number of protons
mass number
protons + neutrons
isotopes
forms of an element with different numbers of neutrons, thus different mass numbers
molecule
a stable association of atoms
orbital
regions where an electron is found 90% of the time
electron shell
a specific sequence inside orbitals; also called energy levels
first electron shell
1 orbital; holds 2 electrons
second electron shell
4 orbitals; holds 8 electrons
third electron shell
4 orbitals; holds 8 electrons
valence shell
determines how the atom behaves; the outermost electron shell
chemical bonds
attractive force that links atoms together to form molecules
covalent bonds
atoms share one or more pairs of electrons so that the outer shells are filled; very strong
electronegativity
attractive force that an atomic nucleus exerts on electrons
nonpolar covalent bonds
electrons are shared equally (atoms have similar electronegativity)
polar covalent bonds
one atom has greater electronegativity, so electrons are drawn more to that nucleus
ionic bonds
when one atom is much more electronegativity than the other, a complete transfer of electrons may occur; formed by electrical attraction of positive and negative ions
ions
electrically charged particles formed when atoms lose or gain one or more electrons
cations
positive
anions
negative
hydrogen bonds
attraction between the - end of one molecule and the + hydrogen end of another molecule
hydrophilic
polar molecules that form hydrogen bonds with water; water loving
hydrophobic
nonpolar molecules, such as hydrocarbon; water hating
van der waals forces
attractions between nonpolar molecules that are close together; brief and weak
