chapter two Flashcards
matter
anything that has mass and takes up space
element
a substance that cannot be broken down into another substance by chemical reactions
atoms
smallest units of elements
- not tiniest particle
molecule
2+ atoms held together by chemical bonds (usually covalent)
compound
2+ different atoms held together by chemical bonds in a fixed ratio
- compounds are molecules
how many elements are essential for life?
- 20-25% of 92 natural elements
- 25 elements for humans
96% of living material is composed of what elements?
carbon, nitrogen, oxygen, hydrogen
trace elements
elements that are required by an organism in minute quantities
- ex. iron, iodine, manganese
3 subatomic particles
proton, neutron, electron
atomic number
number of protons
mass number
protons + neutrons
atomic mass
unrounded neutrons, protons, electrons
- average for all natural isotopes of element
isotope
same number of protons, different number of neutrons
radioactive isotope
isotope where nucleus decays spontaneously and emits energy and particles
useful application of radioactive isotope
PET scans detects location of intense chemical activity
energy
the ability to do work
potential energy
energy that matter possesses because of its location and structure
valence shell
outermost electron shell
electron orbitals
3d space where electron found 90% of time
chemical bonds
attractions that keep atoms together
electronegativity
the attraction of an atom for an electron of a covalent bond
periodic table atoms on the left
have lower electronegativity
- lose e, become cation
- Na, Mg
periodic table atoms on the right
have higher electronegativity
- gain e, become anion
- Cl, F
covalent bond
sharing of electrons
single bond
1 pair of electrons shared
double bond
2 pairs of electrons shared
ex of structural formula
H-H
ex of molecular formula
H(2), C(6)H(12)O(11)
valence
bonding capacity
- number of electrons required to complete valence shell
nonpolar covalent bond
- true covalent bond
- equal sharing of electrons
- H-Hp
when is outer shell full?
8 electrons
when is innermost shell full?
2 electrons
where are polar covalent bonds in relation to water molecules?
within
polar covalent bond
electrons not shared equally
ionic bond
electrons transferred between atoms
- cations/anions formed
where do ionic bonds happen?
between elements that have unequal attractions for valence electrons
ion
charged atom as result of ionic bond
cation
positively charged ion
anion
negatively charged ion
ionic compounds/salts
compounds formed by ionic bonds
- NaCl sodium chloride
- MgCl(2) magnesium chloride
hydrogen bond
weak bond between hydrogen (covalently bonded to EN atom) and another EN atom (of 2nd molecule, usually O/N)
Vand der Waals interactions
ever-changing regions of +/- charge enable atoms and molecules to stick together
- only when close
strength of bonds from strongest to weakest
covalent, ionic, hydrogen, van der waals
function of the molecule is related to what?
shape or size
chemical reactions
making and breaking bonds that leads to a change in composition of matter
reactant
starting materials
product
ending molecules
