Chapter 2: Atoms, Molecules, and Ions Flashcards
law of definite proportions
different samples of the same compound always contain its constituent elements in the same proportion by mass
law of multiple proportions
if two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers
law of conservation of mass
matter can be neither created nor destroyed
matter is made of atoms that are unchanged in a chemical reaction; mass must be conserved as well
atom
the basic unit of an element that can enter into chemical combination
radiation
the emission and transmission of energy through space in the form of waves
electrons
negatively charged particles
radioactivity
spontaneous emission of particles and/or radiation
any element that spontaneously emits radiation is said to be radioactive
alpha rays/particles
positively charged particles; radioactive substances
beta rays/particles
negatively charged particles; radioactive substances
gamma rays
high-energy rays; radioactive substances
Have no charge and are not affected by an external field
nucleus
a dense central core within the atom
protons
positively charged particles in the nucleus
neutrons
electrically neutral particles having a mass slightly greater than that of protons
atomic number
the number of protons in the nucleus of each atom of an element
mass number
the total number of neutrons and protons present in the nucleus of an atom of an element
isotopes
atoms that have the same atomic number but different mass numbers
periodic table
a chart in which elements having similar chemical and physical properties are grouped together
periods
horizontal rows of the periodic table
arranged by atomic number
groups/families
vertical columns of the periodic table
according to similarities in chemical properties