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
metal
a good conductor of heat and electricity
nonmetal
usually a poor conductor of heat and electricity
metalloid
has properties that are intermediate between those of metals and nonmetals
alkali metals
Group 1A elements: Li, Na, K, Rb, Cs, and Fr
alkaline earth metals
Group 2A elements: Be, Mg, Ca, Sr, Ba, Ra
halogens
Group 7A elements: F, Cl, Br, I, At
noble/rare gases
Group 8A elements: He, Ne, Ar, Kr, Xe, Rn
molecule
aggregate of at least two atoms in a definite arrangement held together by chemical forces aka chemical bonds
diatomic molecule
contains only two atoms
polyatomic molecules
contains more than two atoms
ion
an atom or a group of atoms that has a net positive or negative charge
cation
an ion with a net positive charge; loses electron(s)
tend to be formed by metals
anion
an ion whose net charge is negative; gains electron(s)
tend to be formed by nonmetals
ionic compound
formed from cations and anions
monatomic ions
contain only one atom
polyatomic ions
ions containing more than one atom
hydroxide ion, cyanide ion, ammonium ion
chemical formula
express the composition of molecules and ionic compounds in terms of chemical symbols
molecular formula
shows the exact number of atoms of each element in the smallest unit of a substance
true formulas of molecules
allotrope
one of two or more distinct forms of an element
oxygen and ozone are allotropes of oxygen
structural formula
shows how atoms are bonded to one another in a molecule
empirical formula
tells which elements are present and the simplest whole-number ratio of their atoms; not necessarily the actual number of atoms in a given molecule
when analyzing unknown compound, first step is to determine compound’s empirical formula; can deduce molecular formula with more information later
organic compounds
contain carbon, usually in combination with elements such as hydrogen, oxygen, nitrogen, and sulfur
inorganic compounds
organized into four categories ionic compounds, molecular compounds, acids and bases, and hydrates
compounds that DO NOT contain carbon in combination with hydrogen, oxygen, nitrogen, or sulfur
exceptions: carbon monoxide, carbon dioxide, carbon disulfide, compounds containing cyanide group, carbonate groups, bicarbonate groups
binary compounds
compounds formed from just two elements
name: first element is metal cation followed by nonmetallic anion; anion suffix “-ide”
ternary compounds
compounds consisting of three elements
name: Roman numeral indicates number of positive charges of transition metal
acid
a substance that yields hydrogen ions when dissolved in water
oxoacids
acids that contain hydrogen, oxygen and another elements (central element)
often two or more oxoacids have the same central atom but a different number of O atoms
oxoanions
anions of oxoacids
base
a substance that yields hydroxide ions when dissolved in water
Ammonia is classified as a common base because the substances yields hydroxide ions when dissolved in water even though it does not contain hydroxide ions in its structure
hydrates
compounds that have a specific number of water molecules attached to them
