Chem Chapter 3: Properties of Electrons and Light

electrons

are the ultimate determinant of the properties and reactivity of atoms

issac newton

was able to explain how and why rainbows appear

fraunhofer lines

the sun’s rainbow is not continuous but has dark narrow lines called

electromagnetic spectrum

continuous range of radiant energy (also called electromagnetic radiation)

left end of spectrum

shorter wavelengths

higher frequency

higher energy

(violet side)

right end of spectrum

longer wavelengths

lower frequency

lower energy

(red side)

gamma rays, x-rays, ultraviolet rays, visible spectrum, infrared, microwave, radio

what is the order of the electromagnetic spectrum?

visible light

the portion of the electromagnetic spectrum that the human eye can view

wavelengths of visible light

in nm

high energy and shorter wavelength to low energy and longer wavelength

roy g biv

electric and magnetic

what are the perpendicular oscillating fields of radiant energy?

wavelength

the distance from crest to crest or trough to trough

typical units: m to nm

λ

frequency

the number of wave cycles passing a stationary point of reference per unit of time

typical unit: Hz (s^-1)

u

1 wave cycle

1 complete wavelength is…

λu = c (speed of light)

wavelength and frequency are related by…

shorter wavelength

higher frequency =

longer wavelength

lower frequency =

the speed of light

all electromagnetic radiation moves at the same speed, which is?

between energy levels

where can electrons not exist?

energy level

refers to the potential energy associated with an electron/shell in an atom

gets closer together when further from the nucleus

quantum number n

corresponds to the atomic period # (or row on periodic table)

quantum number l

corresponds to the type/shape of orbital

quantum number m_l

corresponds to the electron location within the highest orbital type

pauli exclusion principle

since two electrons cannot occupy the same space at the same time, no two electrons in an atom can have the same four quantum numbers

therefore, each electron has a unique “postal address” to describe its location

aufbau principle

method of building electron configurations by adding one electron at a time as atomic number increases

when adding electrons to an atom electrons always go in lowest energy orbitals available

hund’s rule

add electrons to orbitals singly before pairing electrons in an orbital

2

according to the pauli exclusion principle, what is the maximum amount of electrons per orbital allowed?

s orbitals

shape is a sphere

orbital available for all values of n

the number before the orbital name designates the enrgy level/shell number, n

as n increases, the size of this orbital’s spheres get larger → increasing energy level, increasing distance

3

how many p orbitals are there that exist together

the energy level/shell number

what does the number before the orbital name designate?

d orbitals

only for transition metals or for elements in period 4 and above

5 orbitals

4 of them are shaped like four leaf clovers and 1 is shaped like a p orbital inside a donut

the principal quantum number, n, increases

the energy of atomic orbitals increases as…

the splitting of energy levels

in any atom with two or more electrons, the repulsions between electrons leads to…

the arrangement of electrons in all orbitals

what does an atom’s electron configuration tell?

s block

green

d block

orange

p block

blue

f block

purple

electron configuration shorthand

replace the closest preceding noble gas with its bracketed chemical symbol, then finish configuration

paramagnetic elements

the physical property of being attracted to a magnetic field

property arises due to unpaired electrons in orbitals: the unpaired electron is attracted to a magnet

diamagnetic elements

the physical property of being slightly repelled by a magnetic field

arises due to paired electrons in orbitals

to electrons in an orbital act like magnets paired to each other; it would cost them energy to pull apart from each other

group 2 and noble gases

which two parts of the periodic table will be diamagnetic?

core electrons

electrons in completely filled shells and are stable and don’t interact with other atoms

don’t contribute to the chemical behavior of the element

valence electrons

the electrons found in the outermost shell of an atom

valence shell

the outermost shell

electrons

the number of _____ in the outermost shell of a particular atom determines its reactivity, or tendency to form chemical bonds with other atoms

group number

valence number and ____ number are the same

formation of ions

the gain or loss of valence electrons to achieve stable electron configuration (completely filled shell)

isoelectronic

describes atoms/ions having identical electron configurations

periodic trends in physical properties

atomic radius (atomic size), ionic radius, ionization energy, and electron affinity/electronegativity

periodic trends in chemical properties

periodic trends in reactivity of metals vs nonmetals

atomic radius

the size of an atom is expressed as this

size increases going down a group (up to down = small to large)

size decreases going across a period (left to right = large to small)

because electrons are placed in higher energy orbitals further from the nucleus (number of shells increases)

why does atomic radius increase down a group?

apparent nuclear charge

size decreases across a period due to an increase in…

more attraction of electrons = bigger size

more protons =

smaller

cations are _____ than the atoms they come from

because they lose electrons which loses part of the electron cloud

why are cations smaller than the atoms they come from?

decreases

the stronger attraction pulls electrons closer in towards the nucleus, so size _______

larger

anions are ______ than the atoms they come from

because electrons are added to the outermost orbital, increasing the cloud

why are anions larger than the atom they come from?

increases

since each proton is now pulling on more electrons, it attracts each electron less strongly, so the size of the electron cloud ________

ionization energy

is the energy required to remove an electron from an atom

increases

ionization energy ________ as you go across a period due to valence shell stability

ex: group 17 (-1) is going to be harder to give electrons since it already has 7 valence electrons meaning they are close to achieving a stable noble gas config by gaining one more electron

decreases

ionization energy _______ as n increases because large atoms easily lose electrons (shielding)

electronegativity (X)

a measure of an atom’s ability to attract electrons to itself

uses an arbitrary scale from 0 to 4

fluorine

what is the most electronegative atom?

Cs and Fr

what elements have the lowest electronegativity?

attract electrons

an atom with X near zero has almost no ability to what?

attract electrons

an atom with X near four has a very strong ability to?

increases

ionic radius (size) _____ as you move down a group for metals

decreases

electronegativity _____ as you move down a group for metals

increases

metal reactivity _____ as you move down a group?

increases

ionic radius ____ as you move down a group for non-metals

decreases

electronegativity _____ as you move down a group for non-metals

decreases

non-metal reactivity _____ as you move down a group