Unit 3 chemistry key terms

electromagnetic radiation (EMR)

The energy transferred through space by electromagnetic waves.

electromagnetic spectrum (EMS)

the range of wavelengths or frequencies over which electromagnetic radiation extends.

electromagnetic waves

Waves of energy produced by electrons, can travel through empty space

Regions of electromagnetic spectrum

In order from long/low freq/lowE to short/high freq/highE: radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays

Microwaves uses

Cellphones, cooking, and radar

Radio waves uses

radio, TV, maritime communications, cell phones

infrared waves

Usually given off from the thermal radiation of living things, just below visible light on the EMS

Infrared wave uses

remote controls, checkout scanners, heat lamps

visible light waves

waves we can see; colors of the rainbow; all colors have different wavelengths, and combine to make white light

White light vs ROYGBIV

White (polychromatic) has all of the colors (wavelengths), each color has its own wave length

X-rays and gamma rays

Both used for medical imaging - x-rays can be used to visualise broken bones, Gamma rays are used to detect cancers

Both X-rays and Gamma rays are very penetrative - can easily pass through body tissue

X-rays are reflected by bones which is why we can see them on X-ray images

Gamma ray uses and dangers

Sterilisation ; Cancer, mutation

Thermal radiation is defined as

The type of radiation caused by the object's temperature (as the atoms move and vibrate the electrons move and create waves)

emission spectrum

the spectrum of light released from excited atoms of an element as they go back down to ground state. Our eyes see this as one emitted color - a prism will separate it into colored lines on the visible spectrum

ground state

An electron's "usual" spot in the atom; it's lowest energy most stable state

Excited state

An electron has absorbed energy and jumped up to a higher energy level

Emission

The type of radiation caused by excited electrons releasing their extra energy and returning back to ground state.

Absorption spectrum

The spectrum of visible light absorbed by an atom; shows the "missing" absorbed wavelengths of light as black lines on the colored spectrum.

speed of light equation

c = λv

speed of light

3.00 x 10^8 m/s (all EMR travels at this same speed regardless of where it falls on the spectrum)

Wavelength

Horizontal distance between the crests or between the troughs of two adjacent waves. Unit: meters (m)

Frequency

The number of complete waves that pass a given point in a second. Unit: Hertz (Hz)

Energy per photon

Amount of energy carried by a single photon of EMR

Energy per photon equation

E = hv

Bohr Model

model of the atom in which electrons move rapidly around the nucleus in rings that correspond to a certain amount of energy

quantum mechanical model

the modern description of the behavior of electrons in atoms: Energy levels can be broken down into sublevels that contain a certain amount of orbitals (2 electrons per orbital)

principle energy level

the major energy levels of an atom, corresponding to a "ring" on the Bohr model

Sub levels (s,p,d,f)

a portion of a principal energy level made up of one or more orbitals

Orbitals

A region where an electron will likely be found; up to 2 electrons can reside in each orbital

Aufbau Principle

the rule that electrons occupy the orbitals of lowest energy first (1s, then 2s, then 2p, etc.)

Pauli Exclusion Principle

states that a maximum of two electrons can occupy a single atomic orbital but only if the electrons have opposite spins (Arrows pointing opposite ways in the orbital diagram)

Hund's Rule

within a sublevel, electrons will occupy empty orbitals first before doubling up

electron orbital diagram

a diagram that shows electrons as arrows in the different sublevels

electron configuration

the written form of an orbital diagram; shows how many electrons are in each sublevel

periods on periodic table

A horizontal row of elements in the periodic table

families/groups

Vertical columns on the periodic table

representative elements

an element in the "A" group in the periodic table; as a group these elements display a wide range of physical and chemical properties. The 8 families of the s and p block of the table.

8 representative families of the periodic table

Alkali metals, alkaline earth metals, boron family, carbon family, nitrogen family, oxygen family/chalcogens, halogens, Noble gases

transition elements/metals

Group B elements. Those elements found in the d and f blocks of the periodic table whose properties tend to be less predictable based simply on their position in the table. They all have only 2 electrons and so usually have a +2 ionic charge

valence electrons

The electrons in the outermost shell (highest energy level) of an atom; these are the electrons involved in forming bonds.

octet rule

States that atoms lose, gain or share electrons in order to acquire a full set of eight valence electrons

metallic character

a measure of how easily an element loses a valence electron/reactivity of a metal. Increases as you move left and down the periodic table.

atomic radius

the size of an atom. Increases as you move left and down the periodic table.

ionization energy

the energy required to remove an electron from an atom. Increases as you move right and up the periodic table.

Electron affinity/electronegativity

The attraction an atom feels towards electrons (either to gain electrons or attract them in a bond). Increases as you move right and up the periodic table (except that noble gases are excluded).

Alkali metals

The first column on the periodic table (group 1A), one valence electron (ns1), the most reactive metals, lose 1 electron to have a +1 charge

Alkaline Earth Metals

The second column on the periodic table (group 2A), two valence electrons (ns2), the second most reactive metals, lose 2 electrons to have a +2 charge

The Boron Family

The third A column on the periodic table (group 3A), three valence electrons (ns2np1), lose 3 electrons to have a +3 charge

The Carbon Family

The fourth A column on the periodic table (group 4A), four valence electrons (ns2np2), can either lose 4 electrons to be +4 or gain 4 electrons to be -4

The Nitrogen Family

The fifth A column on the periodic table (group 5A), five valence electrons (ns2np3), gain 3 electrons to have a -3 charge

The Oxygen Family

The sixth A column on the periodic table (group 6A), six valence electrons (ns2np4), gain 2 electrons to have a -2 charge

The Halogens

The seventh A column on the periodic table (group 7A), seven valence electrons (ns2np5), gain 1 electron to have a -1 charge

Noble Gases

The final column on the periodic table (group 8!), eight valence electrons (except He has only 2) so they are already meeting the octet rule and don't gain or lose any electrons.