Chem 1601 Exam 1 Key Terms

significant figures in addition and subtraction

least number of decimal places

significant figures multiplication and division

least number of significant figures

percent error

the percent that a measured value differs from the accepted value

Avogadro's number

6.02 x 10^23

kinetic energy

energy of motion
-electromagnetic
-magnetic
-electrical
-thermal

electromagnetic energy

The energy of light and other forms of radiation.

mechanical energy

Kinetic or potential energy associated with the motion or position of an object

electrical energy

Energy caused by the movement of electrons.

thermal energy

Heat energy

potential energy

stored energy
-gravitational
-electrostatic
-chemical
-nuclear

gravitational potential energy

Potential energy that depends on the height of an object

electrostatic potential energy

arises from the interactions between charged particles

chemical potential energy

Energy stored in chemical bonds

nuclear potential energy

Energy stored in the nucleus of an atom

what happens when bonds are made

energy is released in form of heat

when bonds are destroyed

energy is absorbed

Accuracy

refers to how close a measured value is to an accepted value

Precision

a measure of how close a series of measurements are to one another

extensive property

depends on the amount of matter in a sample

intensive property

a physical property that remains the same no matter how much of a substance is present

Cation

A positively charged ion
-lose electron

Anion

A negatively charged ion
-gain electron

percent relative abundance

the percentage of a particular isotope that occurs in nature

natural abundance

the relative percentage of a particular isotope in a naturally occurring sample with respect to other isotopes of the same element

periodic table groups

elements in same group

have the same number of valence electrons and similar chemical properties

elements in same period

have the same number of electron shells

characteristics of metals

-Malleable: can be formed into thin sheets
-Ductile: can be pulled into thin wires
-Lustrous: have a shiny appearance
-Heat and electricity conductors
-Relatively large densities
-Relatively high melting and boiling points
-All are solids at room temperature, except mercury (Hg)
-Tend to form cations
-Very few colors: grey, silver, gold/copper

characteristics of nonmetals

-Brittle: deform easily, break upon impact, not malleable or ductile
-Dull appearance
-Insulators: poor conductors of heat and electricity
-Relatively lower densities, melting and boiling points than metals
-Various physical states at room temperature
-Tend to form anions
-Variety of colors

alkali metals

Group 1: 1 electron in outer level, very reactive, soft, silver, shiny, low density; Lithium, Sodium, Potassium, Rubidium, Cesium, Francium
-form +1 ions

alkaline earth metals

Group 2 on PT. Two valence electrons, form +2 ions. reactive

Halogens

Contains nonmetals, 7 valence electrons in it's outermost energy level. Very reactive

noble gases

ionic compounds

compounds composed of cations and anions
-held together by electrostatic (or ionic) forces

covalent compounds

typically made of two or more nonmetals and characterized by the atoms sharing their electrons in covalent bonds

Rutherfold's Gold Foil Experiment

positively charged alpha-particles were directed at gold foil, but very few were deflected, leading to the discovery of the nucleus and disproving the Plum Pudding Model
-discovered that atom mostly empty space-since some particles went through.
-some density in middle, since some particles did not get through
-and a + charge since some + alpha particles were deflected awat

law of definite proportions

a given compound always contains exactly the same proportion of elements by mass

Law of Multiple Proportions

if two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers

Metals, nonmetals, metalloids on periodic table

Lanthanides

Actinides

types of bonds in molecular compounds

covalent

basic unit of molecular compounds

molecule

formula of molecular compounds

molecular formula

bonds in ionic compounds

ionic bonds in lattice structure

Basic unit of ionic compounds

The formula unit

formula of ionic compounds

empirical formula

binary acid

an acid composed of only two elements, one of which is hydrogen

oxacids

Acids that are formed by the combination of polyatomic ions with hydrogen ions

alkenes

Hydrocarbons with one or more carbon-carbon double bonds

Alkynes

a carbon compound with a carbon-carbon triple bond.

frequency vs. wavelength vs. energy

-long wavelength=low frequency and low energy
-short wavelength=high frequency and high energy

wavelength

The distance between two corresponding parts of a wave

frequency

the number of complete wavelengths that pass a point in a given time

speed of light equation

c=λv

the order of light on the electromagnetic spectrum

radio waves

Electromagnetic waves with the longest wavelengths and lowest frequencies
-(frequency range: 1 Hz-109 Hz; wavelength range: 1 m-109 m or 109 nm-1018 nm)
-ex: Audio signals, cell phone frequencies, and Wi-Fi communications, MRI

microwaves

the radiation that is primarily associated with heating up food items.
-(frequency range: 108 Hz-1011 Hz; wavelength range: 10-3 m-1 m or 106 nm-109 nm)
-ex: microwave

Infrared

IR light is the energy associated with any warm object, such as the heat that emanates from an electric stovetop or a light fixture
-(frequency range: 1011 Hz-1015 Hz; wavelength range: 10-6 m-10-3 m or 103 nm-106 nm)
-ex:anything that emits heat

Visible region of the electromagnetic spectrum

400-700 nm humans can detect with eyes
-(frequency: ~1015 Hz; wavelength range: 10-7 m-10-6 m or 100 nm-1000 nm)
-ex: ROYGBIV

UV light

invisible light that lies beyond violet. Has higher energy and shorter wavelengths than visible light does.
-(frequency range: 1015 Hz-1017 Hz; wavelength range: 10-8 m-10-7 m or 10 nm-10-2 nm)
-ex: sunlight, tanning booths

X-rays

Electromagnetic radiation having a very short wavelength; can penetrate substances such as skin and muscle.
-(frequency range: 1017 Hz-1019 Hz; wavelength range: 10-11 m-10-8 m or 10-2 nm-10 nm)
-ex: x-ray

gamma rays

Electromagnetic waves with the shortest wavelengths and highest frequencies
-(frequency range: 1019 Hz-1024 Hz; wavelength range: 10-15 m-10-11 m or 10-6 nm-10-2 nm)
-ex: can be used to induce nuclear reactions

photoemission spectrum

When the vapor of an element absorbs incident energy it gives off a unique color, the emitted light is passed through a prism, which can then be used to identify the element, by the colors that are now visible

bohr model of an atom

what is n in the bohr model

When n =1, Bohr's equation computes the lowest possible energy state for the hydrogen atom, called the ground state

what is the excited state in bohr model of an atom?

All states n > 1 are known as excited states

-As n increases, the excited state becomes higher and the further away the electron is from the nucleus.

Bohr frequency condition

an equation derived from the Bohr model of the atom to explain the absorption and emission lines observed from atomic hydrogen.

How does wavelength correspond to length of arrow in Bohr model?

the shortest wavelength is the highest energy, or longest arrow

ultraviolet catastrophe

the failed prediction of classical physics that the energy radiated by a blackbody at extremely short wavelengths is extremely large and that the total energy radiated is infinite

classic wave theory

(photoelectric effect) According to the classical wave theory of light, the intensity of the light determines the amplitude of the wave, increasing the intensity of light (amplitude of the wave) should result in electrons gaining more energy and being ejected from a metal surface with greater kinetic energy in the photoelectric effect

What is the photoelectric effect?

Electrons sitting on the surface of a metal are bound by a binding energy, and light needs to reach a threshold frequency to remove an electron from the metal.

What did the classical model propose about the photoelectric effect?

The classical model suggested that any light with enough intensity can remove an electron from a metal, which is not true in reality.

How does increasing intensity affect the photoelectric effect?

Increasing intensity beyond the threshold frequency ejects more electrons from the metal.

How does increasing frequency affect the photoelectric effect?

Increasing frequency beyond the threshold frequency increases the kinetic energy of the ejected electrons.

Why does each metal have a different threshold frequency in the photoelectric effect?

Each metal has a different threshold frequency because the binding energy varies between metals.

intensity in terms of photoelectric effect

refers to the number of packets of energy

threshold frequency

minimum light frequency necessary to eject an electron from a given metal

3rd Paradox of Physics (Bohr Model)

-Classical understanding: if you shine a light on an element then the element will absorb all light
-In reality: elements only emit light at certain wavelengths and frequencies

Bohr Model of Electron

-Bohr says that without doing anything to an electron it will sit in stationary (n=1) state
>each state (n=1,2,3,4...) have specific energy
-electron can only transition to one state it absorbs EXACT amount of energy
>then when it transitions back it releases exact amount of energy

Energy in Bohr Model

-When electron moves from lower numbered shell to higher number shell energy is absorbed (+)
-When electron moves from higher numbered shell to lower numbered shell energy is released (-)
-As distance traveled by electron increases, energy needed also increases

Higher value of n in Bohr Model

The further the shell is from the nucleus and the higher the energy associated with the shell
-as shell number (n) increases the distance between them decreases

What is the Heisenberg uncertainty principle?

It states that it is impossible to know exactly both the velocity and the position of a particle at the same time.