A substance that cannot be broken down by chemical methods/reactions.
What is the smallest unit of an element?
Atom, because it retain characteristics of that element
What is a compound?
A substance formed by the chemical reaction of two or more elements.
the elements in a compound are combined in fixed ratios
What elements are required for Life?
C, H, N, O
P, S, Ca, K
Na, Cl, Mg
How many of the 92 naturally occurring elements are used by living organisms?
Which of the 4 element are most abundant in cells?
C, H, O, N
What is an Atomic Number?
the # of protons of an element
Atoms of an element have a particular number of protons
Atoms are electricallyneutral.Atomic #= # of protons = # of electrons
How do you find the number of neutrons in an element?
number of neutrons by subtractingatomic # from the mass #
How is the mass # written?
written as a subscript the the left of an element's symbol
What is a Mass number/Atomic Mass?
the # of protons and neutrons
Proton = 1 AMU
Neutron = 1 AMU
Electron have very little mass in comparison
How many electrons does the first energy shell hold?
all other shells hold 8 electrons
What is an orbital?
a three dimensional space that electrons occupy within an energy shell.
How is the periodic table organized?
arranges elements by mass, # of electrons in outer shell, and # of shells.
elements in a same column have similar reactivity
What are isotopes?
atoms with different mass numbers
atoms of an element may not always have the same mass because some atoms have more neutrons than others.
What are the effects of ionizing radiation?
acute, high level exposure can lead to rapid death
chronic exposure can lead to increased incidence of cancer or other disease.
What is ionizing radiation?
energy emitted from decaying radioisotopes
can cause damage
What does Radioactive decay do to an isotope?
Radioactive decay transforms an isotope into an atom of a different element
What do Isotopes do when they decay?
they give off energy AND subatomic particles RADIOACTIVE isotopes are unstable and will "decay"
What arises from unpaired electrons?
reactivity arises from the presence of unpairedelectrons in 1 or more orbitals of valance shells
What are valance electrons?
outer electrons i
What is a valance shell?
outermost electron shell
What are trace elements?
required by an organism in only minute quantities
Ex) Iron (Fe) is needed by all forms of life; others require only by certain species
Is a trace element an essential element?
No it is not an essential element. it is only needed in minute quantities to sustain life.
Which subatomic particals have mass?
Protons and neutrons
What do electrons do in the atomic nucleus?
electrons form a cloud of negative charge around the nucleus
the attraction between opposite charges that keeps the electrons in the vicinity of the nucleus.
What is the mass of a proton and a neutron?
1.7 x 10 -27 gram (g)
instead of grams, when measuring subatomic particles, a dalton or aka AMU, is used instead.
Who is the unit dalton or AMU named after?
John Dalton, a british scientist who developed the atomic theory around 1800
How is the atomic # written?
Atomic # is written as a subscript to the left of the symbol for the element
What is energy?
the capacity to cause change, by doing work
What is potential energy?
the energy the matter processes because of its location or structure.
A lithium atom has 3 protons and 4 neutrons. What is its atomic mass in daltons?
A nitrogen atom has 7 protons, and the most common isotope of nitrogen has 7 neutrons. A radioactive isotope of nitrogen has 8 neutrons. Write the atomic number and mass number of this radioactive nitrogen as a chemical symbol with a subscript and superscript.
1. How many electrons does fluorine have? 2. How many electron shells? 2A. Name the orbitals that are occupied. 4. How many electrons are needed to fill the valence shell?
1. 9 electrons
2. 2 electron shells
2A. 1s 2s 2p (three orbitals)
4. 1 electron is needed to fill the valance shell
1. If two or more elements are in the same row, what do they have in common? 2. If two or more elements are in the same column, what do they have in common?
1. In a row, they share the same # of e- shells
2. In a column, they share the same # of e- in the valance shell
What is a chemical bond?
Atoms "want" to fill their outer most shell
sharing electrons with another atom, giving up and electron, or accepting from another atom
What is Ionic Bonding?
Attraction between two oppositely charged atoms
Atom loses an electron
becomes positively charged ION (cation)
another atom gains an electron and becomes a negatively charged ION (anion)
Result: the two oppositely charged ions are electrically attracted to each other.
What is the strongest chemical bond?
requires a lot of energy, releases energy
when we break those bonds, we release that potential energy
What is a covalent bond?
Two atoms SHARE a pair of electrons
What is Polar Covalent Bonding?
UNEQUALLY sharing of electrons
"Partial" charges denoted by Greek letter lower case delta.
pulled close to the more electronegative atom
What are hydrogen bonds?
formed when a charged part of a molecule having polar covalent bonds forms an electrostatic (charge, as in positive attracted to negative) interaction with a substance of opposite charge.
Molecules that have nonpolar covalent bonds do not form hydrogen bonds.
What is the importance of Hydrogen Bonds?
explains many of the properties of water.
used to stabilize and determine the structure of large macormolecules like proteins and nucleic acids.
involved in the mechanism of enzyme catalysis
What is Van der Waals Interactions?
Weak attractive forces that hold non-polar molecules together
Two atoms come close to each other and electrons fluctuate charges
Helps make sure atoms do not occupy the same space= Repulsion
What is a hydrophobic Interaction?
"scared of water"
nonpolar molecules associate together and exclude water or other polar molecules
What does hydrophilic mean?
What is Amphipathic mean?
molecules that are majority non-polar but have partialpolar charge
What results in Covalent bonding?
formation of covalent bond results in MERGING of the orbitals into 4 new orbitals having a tetrahedral shape.
What shape is a hybrid water molecule?
hydrogen atoms are spread in a V shape at an angle of 104.5 degrees
What is a molecule?
Two or more bonds held together be covalent bonds
Which type of chemical reaction occurs faster at equilibrium, the formation of products from reactants, or reactants from products?
At equilibrium, the forward and reverse reactions occurs at the same rate
What is electronegativity?
the attracting of an atom for the electrons of a covalent bond
What if both atoms are the same?
both have the same electronegativity and share a nonpolar covalent bone