Chemistry - Unit 3: Electrons in Atoms

Scientific notation

• way of expressing very large or very small numbers

• to convert an ordinary number to scientific notation

  • Move the decimal until you have a number between 1 and 9.9999

  • Place a x10 and an exponent equal to the number of times you’ve moved the decimal

  • Exponent is negative if the decimal is moved to the right

  • Exponent is positive if the decimal is moved to the left

standard notation

to convert scientific notation to standard notation:

• move the decimal as many times as the exponent

• move the decimal to the right if the exponent is positive

• Move the decimal to the left if the exponent is negative 

Light

• light is a kind of electromagnetic radiation

• electromagnetic radiation includes many types

  • ie. gamma rays, x-rays, radio waves

• all electromagnetic radiation travels at the same rate (speed of light) when measured in a vacuum

• electromagnetic radiation propagates through space as a wave moving at the speed of light

Speed of Light

c = 2.998 × 10⁸ m/s

λ

lambda, wavelength in meters

ν

nu, frequency in units of seconds or hertz

wavelength and frequency

• wavelength and frequency are inversely related

• As one increases the other decreases

• Different frequencies of light are different colors of light

• the whole range is called a spectrum

J

Joules, unit of energy of a quantum of radiation

Important light equations

c = λv

E = hv

Planck’s constant

h = 6.626 × 10^-34 JS

excited state (atomic state)

atom with excess energy

• atoms absorb energy and become excited

ground state (atomic state)

atom in the lowest possible state

• excited atoms emit photons of light and return to the ground state

atomic orbitals (sublevels)

• within each energy level, the complex math of Schrodinger’s equation describes several shapes

• These are called atomic orbitals

  • Regions where there is a high probability of finding electrons

• Orbitals are s, p, d, and f

  • S —> 1 shape

  • P —> 3 shapes

  • D —> 5 shapes

  • F —> 7 shapes

Aufbau’s principle

electrons enter the lowest energy level first

Pauli Exclusion Principle

at most 2 electrons per orbital

Hund’s Rule

When electrons occupy orbitals of equal energy, they don’t pair up until they have to

Electron Configuration filling order

s → holds 2 electrons max

p → holds 6 electrons max

d→ holds 10 electrons max

f → holds 14 electrons max

Electron Configuration exceptions

• Cr and other elements in its group

  • s¹d⁵

• Cu and other elements in its group

  • s¹d¹⁰

• Half filled orbitals slightly lowers energy

• makes the elements more stable

Ground and Excited electron configuration states

excited→orbitals are not filled fully in order]

ground→orbitals are filled in order

Periods

• horizontal rows

groups

• AKA family

• Vertical columns

• similar physical and chemical properties

Metals

• one of three classes of elements

• electrical conductors, have luster, ductile, malleable

Non-metals

• one of three classes of elements

• generally brittle and non-lustrous, poor conductors of heat and electricity

• some non-metals are gases, brittle solids, and one is a fuming dark liquid

Metalloids

• one of three classes of elements

• properties are intermediate between metals and nonmetals

Alkali Metals

• group 1

• forms a “base” (or alkali) when reacting with water

• excluding hydrogen

Alkaline earth Metals

• group 2

• Also forms bases with water

• do not dissolve well

Halogens

• group 17

• means “salt forming”

Noble gases

• group 18

• previously called “inert gases” because they rarely take part in a reaction

• Very stable → do not react

Transition metals

• block d

• groups 3 to 12

Inner transition metals

• block f

• Lanthanide Series and Actinide Series

Short Hand Electron configuration

start electron configuration from the previous noble gas