Chemistry Midterm review. Units 1-7
percent error
how far off you are from what you should have gotten % error= measured val.- accepted val x 100 accepted val
Empirical formula
"simplest terms" lowest whole number, ratio of atoms in a formula. ex C2H6= CH3 ionic substances are always written empirically
summary of trends: down a group
# of electron shells increases, more shells of electrons "in the way" 1. atomic radius & metallic char. increase 2. I.E. & E.N. decrease
(net) charge of ions
# protons - # electrons
Ionic compounds
(metal + nonmetal); metal TRANSFERS electrons to nonmetal *Rules: same as for ions, subscript becomes # in front of brackets for that ion
Covalent/ Molecular Compounds
(nonmetals); atoms SHARE valence electrons to obtain a complete outer shell
Ions (L-E D)
*Rules 1. Metals: lose electrons (no dots) 2. Non-Metals: gain electrons (octet) 3. [Symbol]^charge
atoms (L-E D)
*Rules: 1. symbol with valence e-'s (dots) 2. pair first two electrons (except group 14), then keep going around
cation
+ ion
anion
- ion
-Periods -groups
-horizontal rows, number of energy levels -vertical columns, elements have similar chemical properties bc they have same number of valence e-'s
*Rules for Covalent/ Molecular compounds
1. 1st atom in the formula goes in the center (except H) 2. Place outer atoms around the center atom 3. Draw in each atom's valence e-'s 4. Connect unpaired e-'s between atoms, with lines 5. Make sure each atom has a total of exactly 8 e-'s (H only 2) 6. Re-draw to place bonds/ electrons as Far Apart as possible (e-'s in bonds repel each other)
density
how much mass is in a given value d= m/v m=d x v v= m/d
shapes of molecules (covalent only)
1. linear: straight across HCl 2. Tetrahedral: 4 sides CH4 3. Bent: H2O 4. Pyramidal: pyramid shaped NH3
to determine number of sig figs
1.circle the digit of precision -no decimal point, rightmost non zero number -decimal point, rightmost digit 2.underline all digits, starting with the 1st nonzero, until the precision runs out
trends in P.T. (2)
1.the greater the nuclear charge (# of protons), the more attracted the electrons are to the nucleus- 1 puppy vs alot of puppies 2. the closer the nucleus(protons), the more attracted the electrons are to the nucleus- sitting in last row vs. front row at concert
mass of water
18 g
ex of # of sig figs 0.023410
5 SF
mol
6.02 x 10^23 things
percent composition
how much of the mass of a substance is made up of one element (or water)
chemical properties
how something interacts with another to become something new
structural formula
how the molecule is written
Guy-Lussac's law
when temp of a gas increases, the pressure increases (direct) P1/T1 = P2/T2
excited state electron configuration
an electron gains energy and "jumps" to a higher energy level (energy of the atom is high and unstable) excited electron releases energy and falls back to the ground state (energy releases light, produces bright line spectrum)
Diatomic elements
Br2, I2, N2, Cl2, H2, O2, F2- "7-H Club", when by themselves (element form) they are in pairs
Charles law
when temp of a gas increases, the volume increases (direct) V1/T1 = V2/T2
State at STP
Gases- noble gases (monatomic), N2, Cl2, H2, O2, F2 Liquids- Br2, Hg (mercury)(metal) Solids- I2, everything else
Nonmetals
Group 17, 18
2 nearly ideal gases are
H2 and He because they are the smallest and have the weakest IMF
Group 18: Noble Gases
NOT reactive (very stable), have 8 valence e-'s (octet rule), except He, monatomic gases
E.N. electronegativity
an atoms ability to attract electrons in a bond with another atom
Ionic Covalent
Roman, no prefixes, numerals Greek, prefixes, no numerals
Polyatomic Ions
Table E; group of covalently bonded atoms that have gained or lost e-'s to form a charged ion
atomic radius & metallic character
Table S. size of an atom how much like a metal an element is. tendency to lose electrons
real gas
actual gas, what we work with in a lab, do not follow the gas laws exactly, particles do attract each other (have some IMF), particles do have some volume...atomic radii
matter
anything that has mass and volume. takes up space
Hydrogen Bonds
are FON; attractions between(not within) molecules that have H bonded to F, O, or N (small, very electronegative atoms)
Dimitri Mendelev Henry Moseley
arranged elements by their properties- Russian chemist developed modern periodic table. British physicist
indirect relationship
as one goes up or down, the other does the opposite
direct relationship
as one goes up or down, the other does the same
Boyle's law
as the pressure on a gas increases, the volume of the gas decreases (indirect) P1 x V1 = P2V2
polar
asymmetrical/ bonds b/w different atoms
Rutherford's Gold Foil Experiment
atoms are mostly empty space, atoms have small, dense, (+) charged nucleus in center
isotopes
atoms of the same element with different numbers of neutrons
ions
atoms with a + or - charge, form when an atom loses or gains e-'s, atoms want to have 8 valence e-'s(most stable. octet rule). will form ions according to this rule, have different chemical properties than they atoms they come from
Intermolecular Forces of Attraction (IMF)
attraction b/w molecules; determine state (solids: stroner IMF- higher b.p.) (gases: weak IMF- lower b.p.); weaker than bonds btwn atoms
ionic bonds
attraction between + and - ions (electrostatic attraction); have ionic character
bonds
attractions that hold atoms or ions together ("simultaneous attraction of 2 nuclei for electrons")
spectral lines
bands of colors produced when excited electrons move from excited state to ground state
ion-molecule attractions
between ions and water molecules, cause solids to dissolve (become aq)
gases are most affected by
changes in pressure, temp, volume
Lewis-electron dot structures (L-E D)
chemical symbol with dots around it to show # of valence electrons; show how e-'s are transferred or shared in a bond
Greek writing chemical formulas
covalent substances (nonmetals only), count metalloids like nonmetals. One words, just write the elements symbol (watch for diatomic elements "7H Club" Br,I,N,Cl,H,O,F). Two Words, the greek prefix becomes the subscript on the element
dependent/ independent
dependent depends on the independent
allotropes
diamond (C), graphite (C) same: element Different: structures/ properties
sig figs
digits recorded in a measurement
entropy
disorder, random-ness. increases when...temp increases, something dissolves *highest in gases*
Wave mechanical model
electrons located in orbitals (clouds) surrounding the nucleus -orbitals= regions of most probable electron location
ionization energy & electronegativity
energy to remove and e- attraction for e- in a bond w/ another atom
Avogadro's law
equal volumes of different gases at the same temp and pressure contain equal numbers of particles
molecular formula
ex. C2H6, regular form
2 ways to separate mixtures
filtration- separates s from L distillation- separates aq (based on boiling pt and uses heat)
Trends in the P.T.
force of attraction= charge of particle 1 x charge of particle 2/ distance between particles squared
Groups 3-12: transition metals
form colored solutions (aq), high melting points (hard metals)
Dalton Rutherford Bohr Current
hard sphere model (cannon ball) discovered nucleus in Gold Foil Experiment Planetary (electron shell) model **Wave mechanical model (electron cloud)(fuzzy cloud)**
Group 2: alkaline earth metals
have 2 valence e-'s, less active (more stable), from ions with a +2 charge
Group 1: alkali metals
have only 1 valence e-, very active (unstable), form ions with a positive 1 charge (+1), found in compounds (bonded to other atoms-more stable) ex. Na in water vs. NaCl in water
ideal gases
imaginary, follow the gas laws, particles NOT attracted to each other, particles have NO volume (negligible)
Romans writing chemical formulas
ionic compounds (metal + nonmetal) (polyatomic ions)
hydrates
ionic compounds that have water molecules attached to the ions and written into its chemical formula
periodic table
it is arranged based on valence electrons in columns
network solids
many atoms bonded at form a giant molecule (macro molecules), very hard solids with high m.p. and b.p. due to strong covalent bonds b/w atoms ex. diamond (C), silicon oxide (SiO2), sand
mass of proton = # of proton =
mass of neutron # of electron
Law of Conservation of Mass
matter cannot be created or destroyed. the number of atoms in the the reactants must equal the number of atoms in the products. both physical and chemical reactions follow this
separating mixtures
mixtures can be separated based on differences in physical or chemical properties
kinetic molecular theory
model that explains ideal gas behavior, 4 assumptions 1. gas particles are in continuous, random, straight-line motions 2. when particles collide, energy is transferred from particle to particle (elastic collisons) 3. gas particles have no attraction to each other (no IMF) 4. individual gas particles have no volume (negligible volume)
Gram-Formula mass
molar mass, GFM, the mass of one mol of a substance. to calculate: add together all the atomic masses of atoms in formula. measured in grams
ground state electron configuration
most stable (lowest energy) arrangement of electrons around the nucleus given on periodic table 1st shell- max 2 e-'s 2nd shell- max 8 e-'s 3rd shell- max 18 e-'s
electricity
movement of electrons
light
movement of light waves
heat
movement of particles, thermal energy
Temperature
not energy, a measure of the "AVERAGE KINETIC ENERGY" of the particles in a sample of matter. measured in degrees Celsius or Kelvins (K)
every atom/ ion has a
nuclear charge equal to the number of protons it has
charge of nucleus
number of protons
summary of trends: across a period
number of protons in nucleus increases, stronger hold/pull on electrons 1. atomic radius & metallic char. decrease 2. I.E. & E.N. increase
physical properties
observed or measured directly
valence electron shell
outermost electron shell, determines chemical properties
metals
positive nuclei surrounded by a "sea" of mobile electrons (moving charges allow for electrical conductivity). left side of staircase. Groups 1-12
2 types of energy
potential- energy of position kinetic- energy of motion
periodic law
properties of the elements are periodic (repeating) functions of their atomic NUMBERS
mass of an element
protons + neutrons
charge on ion
protons- electrons
Physical Changes between states of matter
s to L- melting/ fusion (ENDO) L to g- boiling/ evaporation (ENDO) s to g- sublimation (ENDO) g to L- condensing (EXO) L to s- freezing/ solidifying (EXO) g to s- deposition (EXO)
*Rules from polyatomic ions
same as for covalent compound - add in e-'s in - charge OR subtract e-'s if +charge -put entire ion in brackets w/ charge in upper right corner
covalent formulas (nonmetals)
share electrons
+ ions are - ions are
smaller bc they lose an electron shell bigger bc they gain an electron shell
Metalloids
staircase
STP
standard temperature and pressure, 0 Celsius (273 K), 101.3 kPa (1 atm)
nonpolar
symmetrical/ bonds b/w same atoms
subscript
tells the ratio of atoms in a substance. NEVER change these
coefficient
tells the ratio or reactants to products. change these when balancing the equation
average kinetic energy
temperature
energy
the ability to do work/ to make something happen measured in joules
mass
the amount of "stuff"(or atoms) in a substance
I.E. ionization energy
the amount of energy it takes to remove an electron from an atom in the gaseous state
degrees of polarity
the greater the difference in E.N. values of the atoms, the greater the degree of polarity
ionic character
the greater the difference in E.N. values of the atoms, the greater the ionic character of the bond
precsion
the place value a measurement is made to
stoichiometry
the study of amounts of reactants and products in chemical reactions (study of chemical recipes)
chemistry
the study of matter and energy that makes up the universe
use Table S
to look up values of I.E. & E.N.; to figure out if an element is a s, L, or g as STP (273 K); atomic radius
ionic formulas (metals + nonmetals) (polyatomic ion)
transfer electrons
gases behave most ideally
under condition of high temp and low pressure because: particles are moving faster and farther apart- less chance of gas particles attracting SUMMER
gases deviate from ideal
under conditions of low temp and high pressure because: particles are moving slowly and close together- gas particles attract each other MIDTERMS
K H D B D C M _ _ u_ _n._ _p
units of measurements K= Kilo H= Hecto D= Deca B= Base D= Deci C= Centi M= Mili u= Micro n.= Nano p= Pico
Group 17: Halogens
very active nonmetals, tend to bond with Group 1 & 2 metals, diatomic elements, 7 valence e-'s
average atomic mass
weighted average of all the naturally occuring isotopes of an element to calculate-change % to decimal x mass = products. add all products
when multiplying/dividing- rounding answers with sig figs
your answer needs to have the same # of SF as the given with the least # of SF's provided in the problem
