Chapter 2 - Atoms, Molecules, and Ions Flashcards
law of conservation of mass
mass is neither created nor destroyed.
law of definite proportions
a given compound always contains exactly the same proportion of elements by mass.
law of multiple proportions
a law stating that when two elements form a series of compounds, the ratios of the masses of the second element that combine with one gram of the first element can always be reduced to small whole numbers.
cathode-ray tubes
the “rays” emanating from the negative electrode (cathode) in a partially evacuated tube; a stream of electrons.
electron
a negatively charged particle that moves around the nucleus of an atom.
radioactivity
the spontaneous decomposition of a nucleus to form a different nucleus.
nuclear atom
an atom having a dense center of positive charge (the nucleus) with electrons moving around the outside.
nucleus
an atom having a dense center of positive charge (the nucleus) with electrons moving around the outside.
protons
a positively charged particle in an atomic nucleus.
neutrons
a particle in the atomic nucleus with mass virtually equal to the proton’s but with no charge.
atomic number
the number of protons in the nucleus of an atom.
mass number
the total number of protons and neutrons in the atomic nucleus of an atom.
chemical bonds
the force or, more accurately, the energy that holds two atoms together in a compound.
covalent bonds
a type of bonding in which electrons are shared by atoms.
molecule
a bonded collection of two or more atoms of the same or different elements.
chemical formula
the representation of a molecule in which the symbols for the elements are used to indicate the types of atoms present and subscripts are used to show the relative numbers of atoms.
structural formula
the representation of a molecule in which the relative positions of the atoms are shown and the bonds are indicated by lines.
space-filling model
a model of a molecule showing the relative sizes of the atoms and their relative orientations.
ball-and-stick models
a molecular model that distorts the sizes of atoms but shows bond relationships clearly.
ion
an atom or a group of atoms that has a net positive or negative charge.
cation
a postive ion
anion
a negative ion
ionic bonding
the electrostatic attraction between oppositely charged ions.
ionic solid
a solid containing cations and anions that dissolves in water to give a solution containing the separated ions, which are mobile and thus free to conduct an electric current.
