Chem H Sem 1 Final

units

the amount that a number is referring to

SI system

Mighty King Henry Died Unexpectedly Drinking Chocolate Milk Monday

derived units

units that combine base units through multiplication or division (Ex. volue, density)

volume

length x width x height

density

mass / volume (Ex. g/ml or kg/L)

measurements

using tools and having uncertainties; reported with certain digits and 1 uncertain digit

accuracy

how close measurements are to TRUE VALUE

precision

how closely individual measurements compare to EACH OTHER and how reproducible the measurements are

meniscus

the curve in narrow columns of liquid

percent error

(measured value - theoretical value) / theoretical value * 100

can be positive of negative; no absolute value

significant figures

digits you are certain of + one uncertain digit

Atlantic Pacific Rule

Decimal is Absent:

• Atlantic rule & start with 1st non-zero unit

Decimal is Present:

• use Pacific rule

sig fig add / substract

round the answer to the number with the least number of decimal places

sig fig multiply / divide

round to the number with least number of sig figs

matter

anything that has mass and occupies space

solids

don’t move around, vibrate in place

liquids

flow freely; take shape of container

gases

molecules not attracted, colliding

physical change

rearranges molecules but doesn’t affect internal structure of individual molecules; no new chemicals formed

signs: changes in SIZE, SHAPE, STATE OF MATTER, texture

chemical change

forms new chemical substances, bonds between atoms broken and formed

signs: light emitted, HEAT generated, BUBBLES seen, odor, formation of new SUBSTANCES (precipitate), old substances changes COLOR / shape / mass

law of conservation of matter

states that matter is neither created / destroyed

elements

found on periodic table; can’t be separated into simpler substances with chemical changes

compounds

substances containing 2+ elements; can only be broken down w/ chemical processes

pure substances

made up of same type of atom, molecule, etc.

mixtures

2+ components PHYSICALLY combined; can be separated with physical means

homogenous mixture

evenly distributed physical mixture

heterogeneous mixture

not evenly distributed physical mixture

Democritus

______ proved that matter is made of tiny indivisible particles called atomos and can range in shape.

Dalton

_____ found the Law of Conservation of Matter, compounds, and found that ATOMS are tiny and invisible particles. Also discovered atoms of one element are the same

Thomson

______ discovered the ELECTRON, opposites attract, and protons and electrons even out

J. J. Thomson

Who discovered the Plum Pudding Model and cathode ray tube?

Plum Pudding Model

electrons stuck like pudding

What model is this?

cathode ray tube experiment

electron rays bent toward positive plates and away from negative ones, finding the electron’s charge and proving that atoms are not indivisible

What model is this?

Rutherford

______ discovered the NUCLEUS and PROTONS in the center with electrons orbiting the nucleus

gold foil experiment

What model is this?

Ernest Rutherford

Who conducted the gold foil experiment?

most alpha particles (+) passed through the gold foil, showing that the atom is mostly empty space

some were deflected, meaning there is mass concentrated somewhere in the atom dense enough to deflect alpha particles

What did the gold foil experiment discover?

Bohr

______ discovered electrons lose energy in the light form with different layers and shells

Bohr model

light emission occurs when electron in excited atom drops from higher unstable energy to lower, stable one

exact energy difference released photon of light with specific frequency

What model is this?

line spectra

specific “fingerprints” for each element since only specific energy jumps for electrons allowed

Chadwick

______ discovered the neutron

model of the atom

What model is this?

atomic number

# of protons in an element

neutral atoms

same number of protons and electrons

ions

same number of protons but different amount of electrons

atomic mass

mass of protons + neutrons; 99.7% of mass is in the nucleus so electrons aren’t important (top number)

isotopes

elements with different numbers of neutrons (bottom number)

average atomic mass

multiply mass and natural abundance (%), add it together

characteristics of element

electromagnetic (EM) spectrum

all forms of electromagnetic radiation from increasing wavelength to decreasing

types of waves on EM spectrum

Radio

Microwave

Infrared

VISIBLE

Ultraviolet

X-ray

Gamma

wavelength

What does λ stand for?

electromagnetic radiation

how energy travels through space as a result of photons moving

photons

particles of light, differ from each other by the amount of energy they carry

frequency (v)

measured in cycles / second (Hertz)

number of waves / cycles that pass through a given point in one second

velocity (m/s)

3.00 × 10^8 (all electromagnetic waves) = λ * v

wave energy

diff wavelengths of EM radiation carry diff amounts of energy

formula for energy

Energy = h v (planck’s * frequency)

Planck’s constant (6.63 × 10^-34 Js)

What does h stand for in E = hv?

What is the unit for Planck’s constant?

Joules

What is the unit for frequency?

Hertz

What is the unit for velocity?

m

What is the unit for energy?

same as Planck’s; Joules

continuous spectrum

light can be separated into constituent colors using a prism

line / emission spectra

specific dark / bright lines rather than a continuous spectrum of colors

Balmer Series

set of spectral lines for the hydrogen atom specifically in the visible + ultraviolet light region

results in emission of visible light, causing atomic line spectra

Aufbau principle

states that electron orbitals must be filled from the bottom up (lowest energy level first)

Pauli exclusion principle

each orbital in pairs must have them in opposite spins

Hund’s rule

all orbital levels must be filled singly before doubling up / pairing

noble gas configuration

uses the symbol of the preceding noble gas in brackets to represent the full electron core followed by remaining valence electrons

Ex. [Ne]3s²

excited electron configuration

breaks the Aufbau principle in case of overexciting

quantum mechanical model of the atom

eleectrons do not revolve around nucleus like planets w/ sun, but occupy regions called orbitals

orbitals

region in which electron is most likely to be found

electrostatic repulsion

states that like charges repel

nuclear force

an attractive force that acts between all nuclear particles (protons and neutrons) that are extremely close to each other

radioactive decay

when an unstable nucleus spontaneously disintegrates into something lighter but more stable, emitting particles and electromagnetic radiation

alpha decay

What type of decay emits 2 protons and 2 neutrons?

beta decay

What type of decay emits an electron?

gamma emission

What rays emit high energy EM radiation with no mass (occurs when alpha/beta has excess energy)?

charges of alpha, gamma, and beta particles

What is being demonstrated in this picture?

half life

time required for ½ of the amount of unstable material to degrade into more stable material; pattern is the same but length is different per radioisotope

radiometric dating

process of determining the age of a substance from decay of radioactive elements in the substance

carbon dating

dates organic material up to ~60,000 years old; used on previously alive and relatively material

uranium dating

dates up to billions of years old; usually dates mineral / rocks

groups / families

columns in the periodic table

same amount of VALENCE electrons

periods

rows in the periodic table (your right hand goes left to right when you clock it perioddd)

same amount of electron SHELLS

highest energy electrons in periodic table labeled orbitals

What is being demonstrated?

valence electrons

electrons in the outermost energy level

rule for reactivity and electron configurations

electrons with similar electron config have similar reactivities

alkali metals

Group 1; have a single valence electrons in s orbital

exists in nature in the form of ions with 1+ charge

highly reactive

good conductors of heat / electricity

alkaline earth metals

Group 2; have 2 valence electrons in an s orbital

2+ charge

more reactive than most (but not all) elements

good conductors

transition metals

Group 3 - 12; they’re kinda funny

exist in the d block

inner transition / rare earth metals

most have highest energy electrons in f orbitals

top = lanthanides; bottom = actinides (bottom is w/ uranium)

all lose electrons to form positively charged ions

all actinides radioactive

halogens

Group 17; short 1 valence electrons in a p orbital

1- charge

highly reactive

metallic character

how willing an element is to give an electron away

noble gases

Group 18; full s and p subshells

do not react with other elements

atomic radius

half the distance between 2 nuclei

shielding

when electrons in lower energy levels prevent outer electrons from experiencing the full attractive force of protons

adding an electron to a higher energy level

_______________ increases atomic size.

decreases; # of protons increases attractive force, drawing outer electrons in

Across a period, atomic size ________