Topic 2 Flashcards
atom
the simplest unit of matter
extremely small particles consisting of varying number subatomic particles: electrons, protons, neutrons, and varying atomic number & mass
elements
A substance that cannot be broken down into other substances by ordinary chemical procedures
matter
Any substance in the universe that has mass and occupies space
energy
Energy is needed by all living things to carry out life processes, such as breaking down and building up molecules, and transporting many molecules across cell membranes. It is also responsible for growth and development of a biological cell or organelle. It is carried in the molecule ATP. It is released when a new and strong chemical bond has formed.
electron
subatomic particles with a negative charge, found in orbitals surrounding the nucleus
proton
subatomic particles with a positive charge, found in the nucleus, a mass of ~ 1 Dalton
neutron
subatomic particles with a neutral charge, largest subatomic particle, found in the nucleus, a mass of ~ 1 Dalton
atomic number
will always be equal to the number of protons in the atom
atomic mass
equal to the sum of the atom’s neutrons and protons
ions
atoms with a positive or negative charge
cations
atoms that develop a net positive charge because they lose electrons
anions
atoms that develop a net negative charge because they gain electrons
isotopes
variants of a chemical element that have the same atomic number, but different atomic masses and physical properties. This is because they have the same number of protons but different numbers of neutrons
radioactive isotopes
are unstable and emit radiation as the nucleus breaks up
they lead to cell death in high doses and produce genetic mutations
half-life
the time it takes for one-half of the atoms in a sample to decay.
rate of decay for a radioactive isotope
valence electrons
is the number of electrons an atom/element contains in the outermost electron shell.
octet rule
elements tend to bond in a way that their outer shell of electrons is full (especially C, N, O, & halogens)
inert valence shell
(Nonreactive/noble) elements have their outer valence shell filled, contain all 8 electrons.
chemical bonds
relationships of energy between electrons of the atoms involved
ionic bonds
when one atom donates one or more electrons to another atom forming ions
covalent bonds
involve sharing two or more valence electrons between atoms
hydrogen bonds
weak intermolecular chemical bonds between a partially negative oxygen atom and the partially positive hydrogen atoms of water molecules
polar covalent bonds
a type of covalent bond where the atoms involved have an unequal attraction for electrons, resulting in unequal sharing
nonpolar covalent bonds
a type of chemical bond where the electrons are shared equally between two atoms
electronegativity
an atom’s affinity for electrons, and the differences in electronegativity dictates how electrons are distributed in covalent bonds.
chemical reactions
involves the formation or breaking of chemical bonds, Atoms shift from one molecule to another without any change in number or identity of atoms
the extent of a chemical reaction is influence by temperature, concentration of reactants and products, catalysts
many reactions are reversible
reactants
the original molecules
products
the molecules resulting from the reaction
synthesis reactions
smaller particles are bonded together to form more complex molecules
ex. amino acids into protein molecule
decomposition reactions
bonds in larger molecules are broken, resulting in smaller less complex molecules
ex. glycogen into glucose molecules
exchange reactions
bonds are both made and broken
ex. ATP transfers its terminal phosphate group to a glucose molecule to from glucose-phosphate
cohesion
refers to the attraction between molecules of the same substance. It is responsible for keeping the molecules together and giving a liquid its surface tension
polarity of water allows water molecules to be attracted to one another
adhesion
refers to the attraction between molecules of different substances. It is what causes a liquid to stick to a surface
water molecules stick to other polar molecule by hydrogen bonding
acid
an electrolyte
have a pH range of anything below 7
proton donor
They release hydrogen ions (bare protons) when released in an aqueous solution, dissociate in water
base
an electrolytes
proton acceptors
have a pH range of anything below 7
They pick up hydrogen ions in a solution, when it dissolves in a solution it releases a hydroxyl ion (OH-)
proton donor
acids
proton acceptor
bases
pH scale (acid-base concentration)
measurement of concentration of hydrogen ions [H+] in a solution
The more hydrogen ions in a solution, the more acidic that solution is
pH is negative logarithm (so each pH unit represents a 10-fold difference) of [H+] in moles per liter that ranges from 0-14
Example: a pH 5 solution is 10 times more acidic than a pH 6 solution
neutralization reaction
acids and bases are mixed together
Displacement reactions occur, forming water and a salt
buffers
resist abrupt and large swings in pH
Can release hydrogen ions if pH rises
Can bind hydrogen ions if pH falls
properties of water
High specific heat/heat capacity (prevents sudden temp changes)
High heat of vaporization – useful cooling mechanism for organism
Polar solvent properties – causes ionic substances to dissolve and it forms hydration layers around electrolytes
Reactivity – necessary in reaction (hydrolysis & dehydration synthesis)
Organizes nonpolar molecules – separates hydrophilic and hydrophobic molecules
Forms ions – due to breaking & deforming of the covalent bonds of H2O molecule
Why do carbon atoms tend to make 4 covalent bonds?
Carbon has four valence electrons, and due to the octet rule, it needs 8 to have a full outer shell.
To achieve a stable electron configuration, carbon needs to gain or lose four electrons, which is energetically unfavorable for ionic bonding. So that is why carbon tends to favor covalent bonds, allowing it to form a variety of structures making it a central element in biological molecules.
What determines an element’s reactivity and bonds they form?
valence electrons, stability of the electrons in the atoms, type of chemical bonds it can form
ELECTRONS DETERMINE
chemical behavior of an atom
typically determine by electron arrangement & number of electrons
