Chem Final

Matter

all substances that make up our world, anything that takes up space and has mass, energy is NOT matter

Atom

smallest particle of an element that cannot be chemically or mechanically divided into smaller particles

Types of pure substances

element (all atoms are the same) and compounds (different kinds of atoms)

Element

a pure substance that cannot be separated into simpler substances

Compound

a pure substance composed of two or more elements that are chemically bonded in a fixed proportion

Metallic bonding

weak, not the same as covalent or ionic bonding, can be heated up until different metal types can separate physically

Law of definite proportions

a compound always contains the same proportion of its component elements, ex. Water always has 2 hydrogens per every oxygen no matter its state of matter

Law of multiple proportions

when two elements combine to make two 9 or more) compounds, the ratio of the masses of one of the elements that combine with a given mass of the second element is always a ratio of small whole numbers, ex. CO2 is not the same as CO

Intensive properties

properties that are independent of the amount of the substance

Extensive properties

dependent on the amount of a substance, ex. Mass, volume

Physical properties

properties that can be measured without changing the substance into another substance

Chemical properties

properties that can be observed only by reacting the substance with something else to form another substance

Density

intensive property, the ratio of the mass (m) of a substance or object to its volume (v), d = m/v

Homogeneous mixture

substances are distributed uniformly and the composition and appearance of the mixture are uniform

Heterogeneous mixture

the substances are not distributed uniformly and contain distinct regions of different composition

Solid

has a definite shape and a definite volume

Liquid

has a definite volume but not definite shape

Gas

no definite volume or shape

Energy

the capacity to do work

Work

an exertion of force through distance, w =f x d

Law of conservation of energy

energy cannot be created or destroyed, but it can be converted from one form to another

Potential energy

the energy stored in an object because of its position or composition

Kinetic energy

energy of motion, KE = ½ mu^2

numbers used in counting AND quantities that are assumed to be exact, no fractions or decimals. Metric prefixes are used

Exact values

Measured values

temp. Mass volume, height, pH, etc. needs to have a magnitude and a unit. Uncertainty is always present

SI units

often used by scientists, provides for consistency in measurements

Precision

reproducibility of an experiment

Random errors

uncontrolled fluctuations that occur which affect precision of results, they arise from uncontrollable variables in the measurement

Systematic errors

impact accuracy, can be from a flaw in design, method, equipment, can be corrected

Significant figures

the part of a numerical value you are sure about, give the magnitude of the experiment that you are interested in

Dimensional analysis

a method for converting quantities 9 and other types of problems), conversion factors allow the initial units to be canceled out, leaving the desired units remaining

Atom

the fundamental building block of all matter, made of subatomic particles: protons, neutrons, and electrons, teh # of each of these dictates the properties of the atoms

Isotope

any atom or molecule that has unequal number of protons and electrons

form of element whose atoms have the same number of protons but a different number of neutrons

Average atomic mass

to calculate the average atomic mass (the one found on the periodic table), you sum the products of % abundance x mass isotope

Molecular mass

these are the sum of the atomic mass (from periodic table) that make up a molecule

Mole

unit that allows for quantity values to be more manageable, rather than mass values

Stoichiometry

calculations involving converting from an amount of one substance to the amount of another substance using a stoichiometric ratio (quantity ratio)

Ionic bonds

bonds that can be between both metals and nonmetals, electrons transferred from one atom to another, atoms with opposite charges attract, creates lattice structure

Covalent bonds

bonds can be between nonmetals and metalloids, electrons shared

Metallic bonds

bonds between metals, electrons are delocalized, atoms in metallic solids are held together by a "sea" of mobile electrons that flow freely among all the atoms in a piece of metal, lattice structures

Most commonly occurring polyatomic ions

carbonate/bicarbonate, sulfate, phosphate, nitrate, ammonium, acetate

Naming binary molecular compounds

first word is the name of the first element in the formula, for the second word change the ending of the name of the second element to "ide", use prefixes to indicate the number of each atom , element with smaller group number appears first in formula/name

resonance structures

when there can be more than one lewis structure

Electrostatic attractions

oppositely charged particles are held together by electrostatic attractions between the particles, metal wants to lose electrons and nonmetals want to gain them

Ionic compounds are formed by ions that each have noble gas electron configurations
Formula unit is the lowest whole-number ratio of the ions present

Covalent bonds

formed when two atoms share one or more pairs of electrons equally, the bond length is the distance between the nuclei of two atoms joined together in a bond. The bond energy is the energy required to break one or more covalent bonds

Core electrons

electrons in lower energy levels; spend more time close to nucleus; not very accessible

Valence electrons

electrons in high energy levels; farther from the nucleus; exposed to interaction with other atoms

Valency

the number of covalent bonds that each atom forms is determined by the number of valence electrons that the atom can have in its valence shell

Octet

full valence shell, most stable structures, 8 electrons

Electronegativity

relative measure of the ability of an atom to attract electrons to itself within a bond (covalent)

- Electronegativity increases from left to right and bottom to top of periodic table

- Elements with higher electronegativity are less likely to share electrons and are likely to be the outer atoms in a molecule

formal charges

- The most likely lewis structures are those that have small formal charges or no formal charges, especially for the central atom
- Formal charge = higher electronegativity, while + formal charge = lower electronegativity

exceptions to the octet rule

hydrogen (2 valence electrons), beryllium (4), and boron (6)
Molecules with single unpaired electrons are called radicals

Polarity of a bond

depends on the difference in the electronegativity values of the two elements

Emission spectra

each molecule has a different fingerprint of energy levels

Spectroscopy

the study of the interaction of light with matter

Electromagnetic radiation

an oscillating electromagnetic field that propagates through space

Frequency

the number of waves that pass per unit of time
- When wavelength increases, frequency decreases
- When speed increases, frequency increases
- when energy increases, wavelength decreases

Particle nature of light

light can also be described as a "packet of energy" (a particle) moving through space. We call this a photon. The energy of a photon is related mathematically to its frequency and therefore its wavelength, when energy increases, wavelength decreases

Spectroscopy

- All atoms/molecules have discrete energy levels
- When an atom/molecule absorbs energy, its excited to a higher energy level
- When an excited atom/molecule relaxes back down to a lower energy level, it emits a photon of light
- When an atom/molecule goes between any 2 energy states, it undergoes a transition

Hydrogen atom spectroscopy

- the electron in a hydrogen atom exists on an energy level described using the quantum number n.

- As n increases, energy increases

- Any atom/molecule in its lowest energy level is said to be in its ground state. Any energy levels higher than this is an excited state

- The ground state of H is n=1

Atomic orbitals

electrons , like photons, can be treated as particles or waves

- When we treat them as waves, we use equations called wave functions

- These wave functions essentially tells us all we need to know about the electron, including energy and most probable location around the nucleus

- We can plot the wave functions in a specific way that represents the 3D volume in which we are most likely going to find the electron. These volumes are called orbitals

Principle quantum number (n)

specifies overall energy and size of orbital, possible values are 1,2,3,4,5.... (not 0)

identifies the principal energy level in which the electrons can be found

CORRESPONDS TO: the energy level the electron occupies

l (angular momentum Q.N)

specifies the general shape of the orbital, values can be 0,1,2,3.. Up to (n-1)

CORRESPONDS TO: the type of subshell the electron occupies

ml (magnetic Q.N)

specifies the orbitals general orientation in space, possible values depend on l, can be -l up to +l

CORRESPONDS TO: the orbital the electron occupies

ms (spin orientation Q.N)"

can be ½ or -½
CORRESPONDS TO: the particular electron in a filled orbital

Cations

positively charged by removing an electron, main group elements (s and p blocks), remove electrons in the opposite order they are added, for d and f blocks: remove electrons from the higher n s orbital first

Anions

negatively charged by adding electrons, add electrons to the next available spot as you'd expect

Binary ionic compounds

in the ionic formula, we include the quantity of each ion needed to neutralize the charge

Polyatomic ions

covalent molecules of multiple atoms with extra/fewer electrons to make them an ion , when using in a name, just "copy and paste" into it without any edits

Polyatomic ions we should know

acetate, hydroxide, cyanide, peroxide

Oxyanions

carbonate, chlorate, nitrate, phosphate, sulfate, ammonium, ammonia

Binary covalent compounds

the quantities of each element can vary, since no charges are involved, prefixes are used to denote quantities, add " ide to end"

Prefixes

mono - 1, di - 2, tri - 3, tetra - 4, penta - 5, hexa - 6, hepta - 7, octa - 8 , nona - 9, deca - 10

the "o" or "a" at the end of the prefix is dropped when the element name starts with a vowel

Acids

a covalent molecule that produces H+ when dissolved in water, the formulas often start with H

Binary acids

a single non-metal with H+, ex. HCl - hydrochloric acid, written as " hydro - second element - ic acid"

Oxyacids

acids with oxyanions, if oxyanion ends in "ate" it changes to "ic acid", if ends in "ite" changed to "ous acid"

Empirical formula

a chemical formula that represents the number of each element

Molecular formula

a chemical formula that represents the number of each element

Determining empirical formula

1) calculate the number of moles of each element in the molecule, 2) use appropriate math to scale values up or down to the smallest integers to preserve the ration

Combustion reaction

a reaction between an organic hydrocarbon and oxygen gas (O2), produces carbon dioxide gas (CO2) and water (H2O), and heat

combustion analysis

The C and H in the compound are converted to CO2 and H2O
The masses of Co2 and H2O are then used to determine the masses of C and H in the original sample
If there is a third element in the compound, its mass can be calculated by the difference in mass between the sample mass and the combined mass of C and H in the sample

Dalton's Atomic Theory

matter is made of small particles (atoms) that have properties characteristic of an element
- Atoms contain an equal amount of protons and electrons
- Electrons are a lot smaller than protons and neutrons

atomic number

number of protons in an element, determines the type of element

ions

charged molecules, formed when an atom gains or loses electrons

atomic mass

weighted average of the masses of the naturally occurring mixture of isotopes of an element

period

one of the 7 rows of the periodic table

group

column on the periodic table that includes elements with similar chemical properties

ductile

can be drawn into wire

Wavelength

length of a single wave, measured from one crest to the next, or one trough to the next

- The farther away the crests, the longer the wavelength
- More crests = greater frequency
- Higher the amplitude, higher the energy

Amplitude

height of the wave, determines intensity of the light

Frequency

the number of times a wave crest passes a certain point per second

Photoelectric effect

an experiment that demonstrates the particle nature of light

Threshold frequency

the minimum frequency of light required to eject an electron from the surface of a metal in the photoelectric effect

Light absorption

the process in which the energy of certain wavelengths of light increases the energy of electrons in atoms

Light emissions

the process in which light of specific wavelengths is produced when electrons in atoms fall to lower energy levels

Ground state

lowest energy state of the set of electrons in an atom

Excited state

the state of an atom that has more energy than does its lowest energy state

Ionization energy

the energy required to remove an electron from a gaseous atom to produce a gaseous cation

Rydberg equation

an equation that predicts the wavelengths of a hydrogen atomic emission line

orbital

a region of space in an atom that makes up part or all of a subshell and can hold a maximum of 2 electrons
Subshell: s,p,d,f