Unit 4: Electrons and the Periodic Table

electromagnetic radiation

form of energy that exhibits wave-like behavior as it travels through space

crest (parts of a wave)

top of a wave

trough (parts of a wave)

bottom of a wave

amplitude (parts of a wave)

height of a crest or depth of a trough

wavelength (parts of a wave)

distance of a wave (crest to crest or trough to trough); units = m; variable = λ

equilibrium (parts of a wave)

natural or “rest” position

frequency

# of wave cycles to pass a given point; units = Hz or 1/s; variable = f

velocity

how fast a wave moves from one given point to another; = speed of light (c) = 3.0 x 10⁸ m/s; units = m/a; variable = c

c= λf

speed = wavelength * frequency; wavelength (λ) and frequency (f) inversely related

electromagnetic spectrum

illustrates all forms of electromagnetic radiation

Planck

German physicist; energy changes only in small discrete units, called quantums of energy

E=hf

energy = planck’s constant * frequency; frequency (f) and energy (E) directly related

Planck's constant

6.626x10-34 J/s; variable = h

Joules

unit of energy; unit = J; variable = E

gamma

type of electromagnetic radiation; highest amount of energy; can do most harm

violet

visible color; w/ highest energy

photoelectric effect

electrons emitted from matter bc of absorption of energy from electromagnetic radiation

Einstein (discovery)

light has both wave AND particle properties; beam of light behaves as a wave

atomic emission spectrum

every element emits light when an electric discharge is passed through its gas phase; atoms absorb energy, then release energy through light

principal energy levels

region around the nucleus where the electrons are likely to be moving; more levels → more dis b/w electron + nucleus; contains sublevels

energy sublevels

according to the shapes of the atom’s orbitals

s sublevel

sphere; 1 orbital, 2 electrons

p sublevel

dumbbell; 3 orbital, 6 electrons

d sublevel

clover; 5 orbital, 10 electrons

f sublevel

daisy; 7 orbital, 14 electrons

atomic orbitals

electron probability cloud of an atom’s electrons; may contain at most 2 electrons

electron configuration

shorthand method of writing quantum numbers to represent the arrangement of electrons in atom; all superscripts added = atomic number = # of electrons; last part shows location on periodic table

Aufbau Principle

electrons enter orbitals of lowest energy first (ex: 1s2s2p3s3p4s3d4p; 1s is first)

Pauli Exclusion Principle

1 or 2 electrons per orbital; must spin in opposite directions (opposite spins hold e- in orbital by magnetic attraction)

Hund’s Rule

orbitals of equal energy must EACH have 1 electron with the same spin before any orbital is occupied by a 2nd electron (empty bus seat rule)

electron configuration (coefficient)

represents the energy level

electron configuration (small letter)

represents the sublevel

electron configuration (exponent)

represents the # of electrons

orbital diagrams

visual representation of the electron configuration; each orbital > horizontal line; each line labeled with energy level and sublevel; one electron = one arrow; arrows point opposite directions; include empty orbitals of a sublevel that contains an electron

atomic states

ground or excited state; e- moves; arrangement of the electrons in an atom

ground state

state of lowest energy for an atom (preferred state bc stable); into state releases energy (photon emitted); correct order

excited state

state in which atoms have higher potential energy; into state requires energy; causes electrons to move to higher energy levels

excited state (how to)

light; heat; electricity; electromagnetic radiation

noble gas shortcut

electron configuration; starts at noble gas before element

groups (periodic table)

numbers 1-18 (ones column represents # of valence electrons (electrons in the outermost energy level)); columns; similar physical and chemical properties

periods (periodic table)

numbers 1-7; rows; number of energy levels

blocks of elements (periodic table)

designated by s, p, d, f

zig-zag line (periodic table)

separates metals from nonmetals; metals on left, nonmetals on right

metalloids

along zig-zag line (except aluminum (al)); mostly brittle solids; mixed properties of metals + nonmetals

alkali metals

group 1; except hydrogen; will give up 1 e- to form +1 ion; usually stored under oil bc reacts with water; physical property: soft, silvery metals used in medicine and soaps; most reactive metals

alkaline earth metals

group 2; will give up 2 e- to form the +2 ion; less reactive than group 1 (not as easy to give up 2 e-)

halogens

group 17; will take 1 e- to form the -1 ion; most reactive nonmetals; v close to full valence shell (outer energy level)

noble gasses

group 18; except helium; only needs 2 e- to be full; least reactive group because they have full valence shell (outer energy level)

inner transition elements

metallic elements (outermost f-block); lanthanides (4f), silvery with high melting points; actinides (5f) series, radioactive (>82)

ion

atom (or group of combined atoms) with charge bc of loss or gain of e-

oxidation number

charge of an ion

octet rule

atoms gain or lose electrons to get full valence shell (8 electrons in outer energy level); gets atom the electron configuration of noble gas

atomic radii

distance between nuclei; increases left, down; Adding electrons to higher energy levels; increases the # of energy levels

cesium

largest atomic radius + most reactive metal

ionic radii

distance from the center of the nucleus to the outer edge of the ion

cations (ionic radii)

lose electrons; protons > electrons, protons have more pulling power; results in smaller radius

anions (ionic radii)

gain electrons; Electrons > protons, more repulsion between electrons; results in a larger radius

ionization energy (IE)

energy required to remove the outermost e- from an atom (kJ/mol); to get outer energy level closer to an octet; increases up, right; electrons further from nucleus = easier to take

helium

highest IE

electronegativity (EN)

measure of atom's ability to grab e- from another atom; increases up, right; elements at top of group have e- closely held to the nucleus

fluorine

most electronegative element; most reactive nonmetal

reactivity

refers to how likely an atom is to react with others; depends on how easily electrons can be removed (low IE) + how easily electrons can be gained (high EN)

noble gasses

least reactive group

lanthanides

inner transition element; 4f; silvery with high melting points

actinides

inner transition element; 5f;radioactive (>82)

transition metals

groups 3 - 12; metallic elements; multiple oxidation numbers (states); charges change or “transition”; in d-block