chemical bonds and molecules Flashcards
what is a molecule
2 or more atoms held together by chemical bonds
what is a compound
any molecule composed of 2 or more elements
what is a molecular formula
chemical symbols of the elements in the molecule with the number of each shown (C6H12O6)
what are covalent bonds
when electrons are shared to fill valance shells
what are the 2 types of covalent bonds
- polar covalent
- non-polar covalent
what are hydrogen bonds
when a hydrogen atom from one polar molecule is attracted to an electronegative atom from another molecule
what are ionic bonds
when electrons are transferred, forming ions that are attracted to each other
are covalent bonds strong or weak? stable or not?
strong and energetically stable
when are atoms stable (in a low energy state)
when their outer shell s and p electrons are full
what is electronegativity
a measure of an atoms ability to attract shared electrons towards its own positive charge
what do differences in electronegativity dictate
how electrons are distributed in covalent bonds
what are non-polar covalent bonds
when there is an equal sharing of electrons (balanced)
what are polar covalent bonds
when there is an unequal sharing of electrons (partial positive on one side, partial negative on the other). atoms of different electronegativity
in polar covalent bonds, what element do the atoms tend to be closer to
the more electronegative element
what are nonpolar covalent bonds
bonds between atoms with similar electronegativities. there is an equal sharing of electrons and no charge difference across the molecule
how are hydrogen bonds drawn
as a dotted line
are hydrogen bonds strong or weak
weak electrostatic bonds
what are hydrogen bonds made of
hydrogens with a partial positive charge and other atoms with a partial negative charge (typically oxygen and nitrogen)
what connection do hydrogen bonds have to water
- water molecules interact with one another via hydrogen bonds
- hydrogens with partial positive charges are attracted to oxygens with partial negative charges
- responsible for many of water’s important physical properties
how are hydrogen bonds related to DNA and proteins
they are largely responsible for the structure of DNA and proteins as well as interactions between these macromolecules
how are hydrogen bonds responsible for the structure of DNA and proteins
you can seperate DNA because hydrogen bonds are so weak
what is an ion
an atom or molecule that has gained or lost one or more electrons so the net charge is not neutral
what charge do cations have
a net positive charge
what charge do anions have
a net negative charge
what is an ionic bond
when a cation binds to an anion by electrostatic (charge) attraction
what are the 2 types of ions
- cations
- anions
what are ionic compounds
salts
what is a chemical reaction
when one or more substances are changed into other substances
what is the equation of a chemical reaction
reactants -> products
many chemical reactions often require what?
a source of energy
in order to make chemical reactions, what energy source is often used for living organisms
an enzyme as catalyst
where do chemical reactions most often occur
in liquid (in life- water)
