basic on how atoms bond
atoms with incomplete valence shells interact by either sharing or transferring valence electrons
these interactions typically result in the atoms remaining close together held by an attraction
the sharing of a pair of valence electrons by two atoms
process of covalent bond
if two atoms come close enough that their unshared orbitals overlap, each atom can count both electrons toward its goal of filling the valence shell
two or more atoms held together by covalent bonds constitute this
we can abbreviate the structure of this molecule by substituting a line for each pair of shared electrons drawing this....
indicates the number and types of atoms present in a single molecule
when atoms bond they need to complete their outer valence electron shell
double covalent bond
the sharing of two pairs of valence electrons
every atom has a characteristic total number of covalent bonds that it can from this...
what do covalent bonds form with
they can form between atoms of the same element or atoms of different elements. while both types are molecules, the latter are also compounds. they have to satisfy the valence of both elements.
the attraction of an atom for the electrons of a covalent bond. the strong atoms attempt to pull the shared electrons toward themselves
nonpolar covalent bond
if electrons in a covalent bond are shared equally. this always happens between two atoms of the same element. also between atoms that have similar electronegativities
polar covalent bond
if the electrons in a covalent bond are not shared equally by the two atoms. this happens between oxygen and hydrogen because oxygen has a much higher electronegativity than hydrogen does. these bonds have regions that have a partial negative charge near the strongly electronegative atom and a partial positive charge near the weakly electronegative atom.
this can form if two atoms are so unequal in their attraction for valence electrons that one atom strips an electron completely from the other. because of differences in charge cations and anions are attracted to each other. these atoms need to have not acquired their charge by electrons transferred with each other
where the outer shell has to have eight valence electrons. this happens with every other atom except for hydrogen
where the outer valence electron is filled with only two electrons
after the transfer both atoms are no longer neutral but have charges
atoms with positive charges
atoms with negative charges
compounds formed by ionic bonds. they can have ratios of elements different from 1:1
hydrogen bonds description
within a cell, weak, brief bonds between molecules are important to a variety of processes. these are weak interactions
when a hydrogen atom that is already covalently bonded to a strongly electronegative atom is attracted to another strongly electronegative atom.
chemical bonds are broken and reformed leading to a new arrangement of atoms. all of the atoms in the reactants must be accounted for in the products; they must be balanced
the starting molecules in the process
the end molecule
hierarchy of structural levels
organism level, organ system level, organ level, tissue level, cellular level, molecular level, and atomic level
anything that takes up space and has mass.
is a substance that cannot be broken down to other substances by chemical reactions
carbon, oxygen, hydrogen, nitrogen, phosphorus, and sulfur
elements required by an organism but only in minute quantities
the smallest unit of matter that still remains the properties of an element.
the smaller parts of an atom that make up the atom. ex. protons, neutrons, and electrons.
one unit of a positive charge and makes up the atomic nucleus at the center of the atom. 1 dalton
has one unit of a negative charge and forms a cloud around the nucleus. the attractions between the positive charges in the nucleus and the negative charges of the electrons keep the electrons in the vicinity of the nucleus. 1/2000 dalton but we usually ignore the contribution when determining the total mass of an atom. they have potential energy because of their position relative to the nucleus.
electrically charged neutral and makes up the atomic nucleus at the center of the atom 1 dalton
the unit to measure the mass of subatomic particles
the number of protons and electrons if not indicated otherwise in each element. all atoms of a particular element have the same number of protons in their nuclei.
the sum of the number of protons and neutrons in the nucleus of an atom. therefore we can determine the number of neutrons in an atom by subtracting the number of protons (the atomic number) from this term
atoms of the same element that differ in the number of neutrons
the ability to do work
the energy that matter stores because of it position and location
energy levels/electron shells
the different states of potential energy that the electrons of an atom can have. the first shell, closest to the nucleus, has the lowest potential energy. electrons in outer shells have more potential energy. electrons can only change their position if they absorb or release a quantity of energy that matches the difference in potential energy between the two levels.
the chemical behavior of an atom depends mostly on the number of electrons in its outermost shell. when it is completed it is unreactive. all other atoms are chemically reactive because they have incomplete valence shells.
electrons in the valence shell. atoms with the same number have similar chemical behavior.
the complex three-dimensional space an electron occupies
the hydrogen atom that leaves its electron behind and is transferred as a single proton
the molecule that lost a proton
the molecule with the extra proton
used to describe how acidic or basic a solution is
a substance that increases the hydrogen ion concentration in a solution
any substance that reduces the hydrogen ion concentration in a solution. they have more OH-
product of H+ and OH-
in any solution the concentration is constant at 10-14. in a neutral solution H+=10-7 M and OH-=10-7. they always have to add up to 14 in some way
comparison of H+ and OH-
adding acid to a solution shifts the balance between H+ and OH- toward H+ and leads to a decline in OH-.
reading the pH scale
neutral solutions are 7. acidic solutions have values less than 7 and basic solutions have values more than 7
it occurs when rain, snow, or fog has a pH that is more acidic than 5.6. caused by sulfur oxides and nitrogen oxides in the atmosphere.
most cells are about 80% water
a polar molecule with opposite ends of the molecule with opposite charges. the polarity results from hydrogen bonding
when water molecules are bonded to their neighbors creating a high level of structure. this plays a key role in the transport of water against gravity in plants
clinging of one substance to another
hydrogen bonds among surface water molecules resist stretching or breaking the surface.
how water moderates temperatures on earth
stabilizes air temperatures by absorbing heat from warmer air and releases relatively large amounts of heat with only a slight change in its own temperature.
at seal level water freezes at 0 degrees and boils at 100 degrees. human body temperature averages 37 degrees
as a liquid evaporates the surface of the liquid that remains behind cools. this occurs because the most energetic molecules are the most likely to evaporate, leaving the lower kinetic energy molecules behind
when water reaches 0 degrees celsius water becomes locked into a crystalline lattice with each molecule bonded to the maximum of four partners. therefore its structure makes it float
as ice starts to melt some of the hydrogen bonds break and some water molecules can slip closer together than they can while in the ice state
a liquid that is a completely homogeneous mixture of two ore more substances
the dissolving agent
the substance that is dissolved
water is the solvent
any substance that has an affinity for water. these substances are dominates by ionic or polar bonds
substances that have no affinity for water