enriched chem midterm terms

most if not all of the terms from the terms sheet!!

Chemistry

the study of matter and the changes it undergoes

atom

a collection of protons and neutrons in the center surrounded by a cloud of electrons

Compound

2 or more elements that are chemically bound

molecule

a combination of 2 or more pure substances that are not chemically bound

element

a pure substance with one type of atom

solid

A state of matter characterized by structural rigidity and resistance to changes in shape or volume, where particles are closely packed together.

liquid

A state of matter that has a definite volume but takes the shape of its container, characterized by the ability of particles to flow past one another.

gas

A state of matter with no fixed shape or volume, where particles are far apart and move freely.

change of state

The process in which a substance transitions from one state of matter to another, such as solid to liquid or liquid to gas, often due to changes in temperature or pressure.

physical change

no new substances formed/new molecules, no bonds broken or formed, still the same substance just a different arrangement

Ex: boiling, melting, freezing, condensation, evaporation

chemical change

new substances are formed, bonds are either broken or formed or both

Ex: color/odor change, explosion, transparent to opaque, precipitate formed, bubbles, heat increased or decreased,

group

• Other names: family, column

• 18 columns

• Columns (1A-8A: main group elements) correspond to the number of valence electrons in the periodic table, with similar chemical properties.

• Three major divisions: metals, metalloids, and nonmetals.

period

• Other name: row

• 7 rows

• Corresponds to the number of energy levels contains electrons in their group state in the periodic table, with each period representing elements that have the same number of electron shells.

metals

• (lower, left)

  • Typically solid at room temp.

  • Ductile =  can be made into wire

  • Malleable = bendable 

  • Metallic luster (shiny)

  • Good conductors (heat + energy)

  • Metals tend to lose electrons easily (from cations)

nonmetals

• (higher, right)

  • Can be solid, liquid, and gas at room temp.

  • Dull (not shiny)

  • Brittle (not malleable)

  • Insulators (not a good conductor)

  • Tend to gain electrons (from anions)

metalloids

(zig-zag down from 13th column corner)

• Properties of both metals + nonmetals (in between them)

• Metallic luster (shiny)

• Brittle (not malleable) 

• semi-conductors

filtration

particle size based separation

quantity

The amount or number of a substance involved in a chemical reaction or present in a solution.

SI base units

Base Units:

• Length = meter

• Mass = kilogram

• Time = seconds

• Temperature = kelvin

• Amount of substance = mol

scientific notation

• #’s are wrote in the form m x 10^n for the factor m ≥ 1 and m ≤ 10, n = whole
  #

  • Determine n by counting # places that moved decimal

    • Move left → n = positive

    • Move right → n = negative

volume

The amount of space occupied by an object.

• L x W x H

• m³ or cm³

density

mass/volume

accuracy

The closeness of measurements to the correct or accepted value of the quantity measured.

• close to the accepted value

precision

The closeness of a set of measurements of the same quantity made in the same way.

• closeness to one another (not necessarily the accepted value)

sig figs

rules:

• estimate one place beyond the smallest division

• the last digit contains the uncertainty

• counting zeros: # of digits = # of sig figs

• zeros are counted when:

  • they are between non zeros or sig figs

  • they are after a non zero and a decimal is present

dimensional analysis

symbol	name	conversion
k	kilo	1 kilo - 103 base
h	hecto	1 hecto = 102 base
da	deca	1 deca = 10 base
d	deci	1 base = 10 deci
c	centi	1 base = 102 centi
m	milli	1 base = 10³ milli

atomic mass unit

AMU

a measure of an atoms atomic mass

atomic number

the number of protons

average atomic mass

the average mass of an atom of a given element — abundance a x mass a + abundance b x mass b

avogadro’s number

6.02× 10²³

isotopes

different atoms of the same element with a different number of neutrons

mass number

the number of protons and neutrons combined

the mole

the amount of substance that contains as many particles as there are in 12.0 g of C-12

molar mass

the mass in grams of 1 mole of a substance

mole conversions

bohr

simple model of the atom based on understanding of the sharp line emission spectra of excited atoms

continuos spectrum

A continuous spectrum includes all wavelengths of light without gaps, representing a smooth transition of colors, typically produced by heated solids or liquids.

electromagnetic radiation

A kind of radiation including visible light, radio waves, gamma rays, and X-rays, in which electric and magnetic fields vary simultaneously.

electromagnetic spectrum

• higher frequency = high energy

• long wavelength = low energy

• red (700 μm) → violet (400 μm

• radio → micro → infrared → visible (red → violet) → x-ray → gamma

• low energy/frequency/wavelengths → high energy/frequency/wavelengths

excited state

• emit light of certain wavelengths — this determines its color and depends on the element

frequence

cycles/sec

ground state

lowest possible energy level

speed of light

3.00 × 10⁸ m/sec

planck

Solids emit radiation as heated; study the relationship between wavelength and intensity of radiation emitted and temperature.

planck’s constant

6.625 × 10^-34 j x s

line emission spectrum

when atoms absorb energy, that energy is often released as light energy — when that energy is passed through a prism, a pattern is seen that is unique to that type of atom (this is the emission spectrum)

• falls = emits ⬇

• jumps = absorbs ⬆

• to 1st = UV light

• to 2nd = visible

• to 3rd = IR

photon

electromagnetic energy with the properties of waves and particles

• energy of a photon = hc/λ

quantum

a discrete amount of energy released when an electron rests

wavelength

the space between adjacent waves — λ

photoelectric effect

When light shines on a metal, electrons are ejected from it. (WHY metals appear shiny).

• The ejected electrons have a certain amount of KE

• Depends on wavelength, not intensity

• Proves light not only behaves as waves but also as photons (particles)

heisenberg uncertainty principle

light starts to fan out when it reaches a certain point

orbital

A mathematically described region around a nucleus in an atom or molecule that many contain zero, one, or two electrons.

quantum theory

Quantum objects have both particle-like properties (such as mass, charge, and energy) and wave-like properties (such as wavelength and frequency).

aufbau principle

electrons will occupy the lowest potential energy orbital possible

hund’s rule

aka the roommate rule — all orbitals of equal energy must have one electron before any have 2 electrons

noble gases

• full valence shell (8)

• rare gases

• stable

noble gase configuration

[closest noble gas] rest of electron configuration

pauli exclusion principle

electrons in the same orbital must have opposite spins (beds facing opposite ways)

quantized

electrons could only have very specific amounts of energy and traveled in orbits that were at fixed distances from the nucleus

mendeleyev

made the periodic table — predicted there would be new elements in the spots he had left blank, predicted densities based on properties of other atoms around blank ones

moseley

established the concept of atomic numbers — essentially discovering protons, ordering of the wavelengths of the x-ray emissions of the elements coincided with the ordering of elements based on atomic numbers

actinide

Inner transition metal: A series of metallic elements (atomic number 89 - 103).

• Radioactive

• Soft, shiny, silver-colored

• All radioactive

• First four are naturally found, the rest are lab-made

lanthanide

Inner transitional metal: A series of metallic elements( atomic number 58-71).

• All very similar in properties

• Shiny metals

• Similar reactivity of that of alkaline earth metals

periodic law

states that the properties of elements are periodic functions of their atomic number

alkali metals

• Valence e-  configuration = 1 val e-

• Soft, silvery, shiny

• Highly reactive (not free elements in nature, always found w/ another element)(lose e- easily)

alkaline metals

• Valence e-  configuration = 2  val e-, s²

• Less reactive than 1A (still too reactive to be found free in nature)(lose e- easily)

  • Forms bases when it reacts with water

• Harder, denser, higher melting point than 1A

• Moderately metallic

halogens

• salt formers (with alkali’s)

• brinclhoff’s: gases found diatomically in nature: Br, I, N, Cl, H, O, F

• most reactive nonmetals

transition metals

good conductors, harder, denser, higher melting point than s and p block elements, less reactive than s block elements

metals lose electrons to form positive

cations

nonmetals gain electrons to form negative

anions

shielding effect

the repulsion of outer electrons by inner electrons

• F = (+ charge) (- charge) / r²

effective nuclear charge (z*)

net positive charge that is attracting a particular electron

• protons - inner electrons

atomic radius

size of the atom

• get smaller as you go from left to right

• the more electrons you add, the more protons are attracted

• the bigger they are, the weaker they hold their electrons

ionic radius

The distance between the nucleus of an ion and the outermost shell of the ion.

ionization energy

energy that an atom needs to absorb in order to lose an electron

successive ionization energies

each successive removal of electron requires more energy than the last with it having a sizeable energy cost for the inner shell electrons

valence electrons

electrons in the highest energy levels s and p subshells (lose or gain to complete shell — except for noble gases)

electronegativity

the strength an atom has when attracting electrons in a bond

• increases as you go up and to the right

reactivity

• metals have a low Ionization energy and lose electrons to become smaller cations, reactive, conductive, not brittle

• nonmetals have high electron affinities and gain electrons to become larger anions, brittle not conductive

metallic character

The level of reactivity of a metal (increases going down + right).

• Metals tend to lose electrons in chemical reactions (due to low ionization energies and low electronegativities) 

chemical bond

Hold molecules together and create temporary connections that are essential to life.

ionic bonds

when one electron is transferred from one atom to another resulting in oppositely charged particles with an attraction to each other (between a metal and a nonmetal)

covalent bond

2 elements of similar strength and electronegativity, nonmetals (some metalloids) sharing electrons

nonpolar covalent

electrons shared equally

polar covalent

electrons shared unequally

bond polarity

Describes how the electric charge is distributed across a chemical bond between two atoms.

molecular compound

A chemical compound is made up of two or more nonmetal atoms that are held together by covalent bonds.

• Shares electrons

• Lowers melting points/boiling points because they’re easier to break

chemical formula

Tells us the number of atoms of each element in a compound.

formula unit

ratio of atoms

octet rule

atoms must have a complete valence shell (8 electrons)

lewis dot structures

A diagram that shows how electrons are arranged around atoms in a molecule.

single bond

longest, weakest, 2 electrons

double bond

in between strength and length, 4 electrons

triple bond

6 electrons, shortest, strongest

lattice energy

energy released when 1 mole of an ionic compound forms from its ions

VSEPR theory

Valence Shell Electron Pair Repulsion → molecule adopts the shape that minimizes the electron pair repulsions.

molecular shapes

• Electron Pair Geometry: lone pair on central atom + atoms bonded to central atom

  • 2 = Linear: 180º

  • 3 = Trigonal-planar: 120º

    • Trigonal-planar (e- pair geometry) + bent (molecular geometry): <120º

  • 4 = Tetrahedral: 109.5º

    • Tetrahedral (e- pair geometry) + Trigonal-planar (molecular geometry): <109.5º

    • Tetrahedral (e- pair geometry) + Bent (molecular geometry): <<109.5º

polarity

The polarity of each molecule has to do with the unevenness of electron distribution.    

• Polar = a positive side and a negative side

• Nonpolar = symmetrical, no positive + negative charge (they cancel each other out)

dipole

•  integrates polarity/asymmetry (point towards negative)

  • Lone pair = negativity 

  • Shown through an arrow pointing to the negative side

intermolecular forces

the attractive and repulsive forces that arise between the molecules of a substance