is the study of matter and the changes it undergoes
Matter
is anything that occupies space and has mass
Substance
is a form of matter that has a definite composition and distinct properties
Mixture
is a combination of two or more substances in which the substances retain their distinct identities
Homogeneous mixture
composition of the mixture is the same throughout eg. soft drink, solder
Heterogeneous mixture
composition is not uniform throughout eg. iron filings in sand Milk
Physical means
can be used to separate a mixture into its pure components
Element
a substance that cannot be separated into simpler substances by chemical means
118 elements have been identified
82 elements occur naturally on Earth eg. gold, aluminum, lead, oxygen, carbon, sulfur
36 elements have been created by scientists eg. technetium, americium, seaborgium
Compound
is a substance composed of atoms of two or more elements chemically united in fixed proportions
Compounds can only be separated into their pure components (elements) by chemicalmeans
Molecule
is an aggregate of two or more atoms in a definite arrangement held together by chemical forces
Diatomic molecule
contains only two atoms eg H2, N2, O2, Br2, HCl, CO
Polyatomic molecule
contains morethan two atoms eg O3, H2O, NH3, CH4
Ion
is an atom, or group of atoms, that has a net positive or negative charge
Cation
Ion with a positive charge
If a neutral atom loses one or more electrons
it becomes a cation
Anion
Ion with a negative charge
If a neutral atom gains one or more electrons
it becomes an anion
Monatomic ion
contains only one atom eg Na+, Cl- , Ca2+, O2- , Al3+, N3-
Polyatomic ion
contains morethan one atom eg. OH- , CN- , NH4 +, NO3 -
Ionic compounds
consist of a combination of cations and an anions
Chemical Bonds
net forces of attraction that hold atoms together
CovalentBond
sharing of e-
atoms of non-metals combine
electronegativity difference is 0 to < 2
Electronegativity
is the ability of an atom to attract toward itself the electrons in a chemical bond
IonicBond
attraction between cations and anions
atoms of metal and nonmetal combine
metals lose e- (cations), nonmetals gain e- (anions)
Valenceelectrons
are the outer shell electrons of an atom. The valence electrons are the electrons that participate in chemical bonding
LewisDotSymbol
Consists of the symbol of an element and 1 dot for each valence e- in an atom of the element
Octet Rule
Observed tendency of atoms (representative elements) to lose , gain or share e- in order to acquire an octet e- in their outermost main energy level
ValenceShellElectronPairRepulsionTheory (VSEPR)
Determines the shape of the molecule
Polar
unequal distribution
different elements
non-metal
Non-polar
equal distribution
same elements
non-metal
Intermolecular Forces ofAttraction (IMFA)
Attractive forces between molecules
Dipole-dipole forces
between polar (covalent) molecules
greater than 0.5 en
opposite attracts
Ion-dipole forces
attraction between an ion (cation or anion) and a polar molecule
Londondispersionforces
Van der Waals interaction
attractive forces in all (covalent) molecules
Ion-ionforces
Electrostatic forces
Attractive forces between cations and anions in ionic compounds
Hydrogen bond
special type of dipole-dipole interaction between the H atom in a polar bond and an electronegative O, N or F atom
Self-assembly
The self-organization of components into patterns of structures without human intervention due to different kinds of interactions happening among the components
Molecularself-assembly
involves the Van der Waals interaction, electrostatic, hydrophobic, hydrogen bonds, and coordination bonds
Macroscopicobjects
involves gravitational interaction, external electromagnetic field, capillary, and entropic interaction
Staticself-assembly
System that are at local equilibrium and do not dissipate energy