Suzanne D'Anna1 Molecules Compounds Chemical Reactions

Suzanne D'Anna2 Molecules l two or more of same or different elements chemically combine H (atom) +H (atom) H 2 (molecule)

Suzanne D'Anna3 Compounds l two or more different atoms combine together to form a molecule called a compound 4H (atoms) + C (atom) CH 4 (molecule) (methane)

Suzanne D'Anna4 Chemical Reactions l when atoms combine or dissociate from other atoms: - new products are formed - chemical reactions are foundation of all life processes Chemical Bonds l formed when atoms unite chemically

Suzanne D'Anna5 Bond Formation l energy relationship (not physical) l involves reactions between electrons of reacting atoms l electrons in outermost shell are most important in bonding

Suzanne D'Anna6 Electrons l occupy specific regions in rotation around the nucleus of an atom l these regions vary in distances from the nucleus l each orbit around nucleus represents one electron shell or energy level

Suzanne D'Anna7 Electrons (cont.) l each shell holds a certain maximum number of electrons l innermost shell nearest nucleus never holds more than 2 electrons l second shell holds 8 (rule of 8’s) l third 18 l higher shells (7) hold many more electrons

Suzanne D'Anna8 Stability l atoms will react to maintain 8 electrons in their valence shell (except shell one which is full at 2 electrons) l if valence shell has less than 8 electrons the atom will gain, loose, or share electrons to remain stable

Suzanne D'Anna9 Electrons l electrons in energy level closest to nucleus are most strongly attracted to its + charge l electrons farthest from nucleus or + charge are most likely to react with other atoms

Suzanne D'Anna10 Bonding l most important electrons are those in outermost shell (valence shell) l inner shells do not necessarily take part in bonding

Suzanne D'Anna11 Types of Chemical Bonds

Suzanne D'Anna12 Ionic Bonds l formed when electrons are completely transferred from one atom to another l during bonding atoms gain or loose electrons l therefore atoms are no longer neutral l now called ions

Suzanne D'Anna13 Ions l are atoms that have gained or lost electrons l negatively or positively charged particles l Two types of ions: - anion (-) atom that has gained electrons - cation (+) atom that has lost electrons

Suzanne D'Anna14 Electrolytes l are ions in solution l ionic solution is capable of conducting electrical current

Suzanne D'Anna15 Sodium (atomic number = 11) l valence shell has 1 electron l incomplete l if 1 electron is lost it will have more protons than electrons l + charge l cation

Suzanne D'Anna16 Chlorine (atomic number = 17) l valence shell has 7 electrons l incomplete, needs one electron to fill valence shell l if 1 electron is gained it will have more electrons than neutrons l - charge l anion

Suzanne D'Anna17 Ionic Bond - Sodium Chloride l sodium tends to give up its single electron in its valence shell l chlorine will pick up one electron to completely fill its valence shell

Suzanne D'Anna18 Covalent Bonds

Suzanne D'Anna19 Covalent Bonds l bonds in which atoms share electrons l more common bond in the body than ionic l electrons of combining atoms are neither lost or gained l electrons are shared

Suzanne D'Anna20 Single Covalent Bond H 2 (H H) l when two atoms share one pair of electrons (H-H) l valence electrons are shared l shared electrons orbit whole molecule and satisfy stability needs of both hydrogen atoms

Suzanne D'Anna21 Double Covalent Bond Oxygen (O O) l occurs when two atoms share two pairs of electrons

Suzanne D'Anna22 Triple Covalent Bond Nitrogen (N N) l occurs when three pairs of electrons are shared

Suzanne D'Anna23 Nonpolar Covalent Bonds l electrons are shared equally between two atoms l strongest of all chemical bonds l electrons spend approximately equal time around each nucleus l Example: - carbon:carbon, and hydrogen:hydrogen bonds are nonpolar covalent

Suzanne D'Anna24 Polar Covalent Bonds l unequal sharing of electrons between atoms l one atom attracts shared electrons more strongly than the other l Example: - hydrogen and oxygen in a molecule of water

Suzanne D'Anna25 Hydrogen Bonds l attraction between partially ( - ) or ( + ) charged atoms l Examples: - exist between adjacent H 2 O molecules - between polarized regions of same large molecules (protein) - between two strands of a DNA molecule

Suzanne D'Anna26 Chemical Reactions

Suzanne D'Anna27 Chemical Reactions l involved in making or breaking bonds between atoms l new bonds are formed l total amount of atoms remains the same l new arrangement or combination

Suzanne D'Anna28 Synthesis Reaction (anabolism) l two or more molecules or reactants bond together to form larger complex molecule l involve bond formation l energy-requiring reaction l growth/constructive l repair

Suzanne D'Anna29 Synthesis Reaction (anabolism) l A + B AB l 2H + O H 2 O

Suzanne D'Anna30 Decomposition Reaction (catabolism) l molecule is broken down into smaller parts l synthesis reaction in reverse l energy is released l destructive l Example: - digestion of foods into building blocks

Suzanne D'Anna31 Decomposition Reaction (catabolism) l AB A+B l NaCl Na + + Cl -

Suzanne D'Anna32 Exchange Reaction l involve synthesis and decomposition reactions l bonds are made and broken l molecule parts switched

Suzanne D'Anna33 Exchange Reaction l AB + CD AD + CB l Example: - iron-containing complex in RBC unloads carbon dioxide and picks up oxygen in lungs.