Download Chapter 5 and 6 Notes 2015-2016 Models, Waves and Light Models

Chapter 5 and 6 Notes 2015-2016
Models, Waves and Light
Models:
 Each new model contributed to the model we use today. Even our current Quantum
Mechanical model, does not give us an exact model of how _____________ interact.
Quantum Mechanical Model of the Atom
• Quantum Mechanical Model is the current description of electrons in atoms.
– It does not describe the electron’s ______________________ around the nucleus
• Quantum Mechanical Model based on several ideas including:
– Schrodinger wave equation (1926) is mathematical equation describing the
behavior of an electron and treats electrons as _________________________.
 Heisenberg uncertainty principle (1927) states that it is impossible to know both the
____________________ and ______________________________of a particle at the
same time.
Atomic Emission Spectrum
 When a current is passed through a vacuum tube of gas at low pressure, a set of
_________________ of the electromagnetic waves are emitted by atoms of the element
 Used to determine which elements are present in a sample
 Used to determine which elements are present in a star
 Each element has a _________________ spectrum
 Only certain _________________ are emitted meaning only certain frequencies of light
are emitted
Spectroscope
 A spectroscope that has a diffraction grating is needed to see the atomic emission
spectra, which acts similar to a prism, separating different _________________ of light
1
Explanation of Atomic Spectra
 Electrons start at its lowest energy level (ground state)
 When an e- absorbs energy it moves to a higher energy level (excited state)
 When the e- drops back down to a lower energy level, it gives off a quantum of energy called a
“_____________”
 Only certain atomic _____________are possible and emitted
Photons behave like ____________ and waves
Electromagnetic Spectrum
 Electromagnetic spectrum is the range of all energies emitted from photons acting like
_____________.
 If it is not in the visible light range, it may be giving off other forms of electromagnetic
radiation like radio, microwaves, infrared, ultra violet, x-rays, or _________________ rays
Visible Light Spectrum
Characteristics of a Transverse Wave
 Wavelength  (lambda) – shortest ____________________ between equivalent points
on a continuous wave [Unit = meters]
 Frequency  (nu) – the ____________________ of waves that pass a given point per
second [Unit = 1/second = s-1 = Hertz (Hz)]
 Crest – _____________________ point of a wave
 Trough – ____________________point of a wave
 Amplitude (a)– height from its origin to its crest (highest point) or trough (lowest point)
2
Wavelength and Frequency
 Wavelength () and frequency () are related
 As wavelength goes up, frequency goes down
 As wavelength goes down, frequency goes up
 This relationship is _____________________________ proportional
What is the length of a wave? Frequency of a wave?
 Formula: c = 
 Speed of light (c) = 3 x 108 m/s
  = wavelength,  = frequency
Practice 1: Calculate the wavelength () of yellow light if its
frequency () is 5.10 x 1014 Hz.
Practice 2: What is the frequency of radiation with a wavelength () of 5.00 x 10-8 m?
What region of the electromagnetic spectrum is this radiation?
How Much Energy Does a Wave Have?
 Energy of a wave can be calculated
 Formula: E= h
 E= Energy,  = frequency
 h = Planck’s constant = 6.626 x 10-34 Joule . Sec
 Joule is a unit for energy (J)
 Energy and frequency are directly proportional, as frequency increases, energy _______
 Energy of a photon given off by an electron going to a lower energy level is E =h
Practice 3: How much energy is given off by a wave with a frequency () of 2.0 x 108 s-1?
( h = 6.626 x 10-34 J.s)
Visible Light, Frequency, and Energy
 Red _________________ wavelength (), smallest frequency ()
 Red frequency smallest (), least amount of energy (E)
 Violet smallest wavelength (), largest _________________ ()
 Violet frequency largest (), greatest amount of energy (E)
3
Noble Gas Configuration
REVIEW: Electron Configurations
A. Principal energy levels: n = 1 to 7 (row # in the periodic table)
B. Energy sublevels: s,p,d,f
C. Orbitals:
describes the electron’s ________________
orbitals are not necessarily ________________
maximum of 2 electrons per orbital: s = 2, p= 6, d = 10, f = 14
Example: Sodium(Na) -11 electrons = 1s22s22p63s1
What are Noble Gases?
• Noble gases are found in group _____________
• The elements are called noble because they are non-reactive and very
__________________.
• The do not tend to form compounds
Noble Gas Configuration
Element Electron
What is in common? Noble Gas
Configuration
Configuration
2 2
6
2 2
6
Ne
1s 2s 2p
1s 2s 2p
Don’t abbreviate
noble gases
1s22s22p6
Mg
1s22s22p63s2
1s22s22p6 = [Ne]
[Ne] 3s2
Which Noble Gas is Used?
• To figure out which noble gas to use find the noble gas that is closest to the element
without going over in atomic number
• Which noble gas is closest without going over?
• Rb : ____
Cl : ____
Ra : ____
Practice
• Write the closest noble gas without going over in brackets.
• Write any remaining electrons not accounted for in the noble gas after the brackets
Write the noble gas configuration of the following elements.
Element
Closest
Noble gas
without
going over
Noble Gas
Configuration
Element
Mg
Cs
Ca
Si
N
S
Co
Ti
Zn
Br
Sn
Se
4
Closest Noble
gas without
going over
Noble Gas
Configuration
Development of the Modern Periodic Table
Early Periodic Table – Atomic Number
• In 1913 Henry Mosley discovered that each element contained a unique number of
protons in the nuclei
• Arranged elements in order of atomic ___________________________.
• Resulted in a clear periodic pattern of properties.
Periodic Law
• There is a periodic repetition of chemical and physical _______________________ of
elements when arranged in increasing atomic number (increasing number of protons) is
called the periodic ___________
Modern Periodic Table
• Organized in columns called _________________ or families
• Rows are called ________________________
• Group A – representative elements (1A-____________)
• Group B - ___________________ elements (1B-8B)
Classification of Elements
• Three classifications for elements metals, nonmetals, and metalloids (semimetals)
Metals
• Properties of Metals
– shiny, smooth, clean solids (except mercury)
– __________________conductors of heat and electricity
– High ______________________
– High melting and boiling points
– ______________________ – bended or pounded into sheets
– Ductile – drawn into _________________
Groups of Metals
• ______________________ metals – group 1A except H
• Alkaline earth metals – group ____________
– Alkali metals and alkaline earth metals are chemically reactive
• Transition metals – group __________ elements
• Inner transition metals
– Lanthanide
– Actinide
5
Organizing by Electron Configuration
• Group number for group A elements represents the number of ___________________
electrons
• Atoms in the same group have similar chemical properties because they have the
same number of valence electrons
Alkali Metals
• Electron configurations for alkali metals
• Lithium
________________
[He]2s1
• Sodium 1s22s22p63s1
[Ne]3s1
• Potassium 1s22s22p63s23p64s1
[Ar]4s1
• Rubidium 1s22s22p63s23p64s23d104p65s1 [Kr]5s1
• What do the four configurations have in common?
• They have a _____________________ electron in their outermost energy level
• They all have one valence electron, thus similar chemical properties
Alkaline Earth Metals
• Electron configuration for alkaline earth metals
• Beryllium
[He]2s2
• Magnesium
[Ne]3s2
• Calcium
[Ar]4s2
• Strontium
[Kr]5s2
• All alkaline earth metals have _____________ valence electrons, thus similar chemical
properties.
Nonmetals
• Gases or brittle, dull looking solids
• ______________________ conductors of heat and electricity
• Usually have lower densities, melting point, and boiling point than metals.
• Groups of nonmetals
– Halogens ____________
– Noble gases ____________
Noble Gases
• Noble gases – Group _______________
• Called inert gases because they rarely take part in a reaction
– He – 1s2
– Ne – 1s22s22p6
– Ar – 1s22s22p63s23p6
– Kr – 1s22s22p63s23p63d104s24p6
6
• Because noble gases have completely filled s and p sublevels, they do not react
with other elements
Metalloids aka Semi-metals (pink)
• Physical and chemical properties similar to both metals and nonmetals
• They are metallic-looking _________________ solids
• Relatively good electrical conductivity.
• Used in glasses, alloys, and semiconductors
• The six elements commonly recognized as metalloids are boron, silicon, germanium,
arsenic, antimony, and tellurium. Polonium and astatine are sometimes classified as
metalloids
Periodic Trends
Atomic Radius
• Defined as half the distance between two bonding atoms nuclei
(since electrons do not have a clearly defined edge)
Atomic Radius Across a Period
• Atomic radius generally ___________________________ in size as you move left to
right across the period
– ___________________ positive charge in the nucleus pulls the electrons of the
same energy level in.
7
Atomic Radius Down a Group
• Atomic radius _______________________________ as you move down a group
– Orbital size increases as you move down a group with increasing energy level
– Larger orbitals means that outer electrons are _____________________ from the
nucleus. This increased distance offsets the greater pull of the increased nuclear
charge.
– As additional orbitals between the nucleus and the outer electrons are occupied,
the inner electrons shield the outer electrons from the pull of the nucleus this is
called _______________________
• Shielding
– The inner electrons shield the outer electrons from feeling the pull of the nucleus
Cation and Anion
• An ion is a positively or negatively charged atom that gains or loses an
___________________________.
• A cation loses electrons and produces a _________________________ charge
• An anion gains electrons and produces a _________________________ charge
Ionic Radius - Cations
• Groups 1A, 2A, 3A, and other metals tend to_____________________ electrons and
form cations.
• When atoms lose electrons they become __________________________
– The electron lost will be a valence electron leaving a completely empty outer
orbital
– Protons in nucleus can pull fewer electrons tighter
8
• These atoms lost electrons and became _______________ cations.
Ionic Radius - Anions
• Group 5A, 6A, and 7A tend to ________________________ electrons and form anions
• When atoms gain electrons and form negatively charged ions, they become
________________________.
– Protons in nucleus have more electrons to pull and cannot pull in as tight
• These atoms gained electrons and became ____________________ anions
Ionization Energy
• The energy required to _________________________ an electron from a gaseous atom
• Indication of how strongly an atom’s nucleus holds onto its
__________________________electron
• Groups 1A, 2A, and 3A tend to have low ionization energies because they want to lose
electrons.
Ionization Energy Trends – Across a Period
• Ionization energy ________________________as you move left to right
– Across a period electrons are added to the same energy level (same distance away from
the nucleus), yet the nuclear charge is increasing across a period increasing the
attraction to the electrons.
Ionization Energy Trends – Down a Group
• Ionization energy __________________________ as you move down a group
– Down a group electrons are added to a higher energy level (farther distance away from
the nucleus), making it easier to remove an electron
Octet Rule
• Sodium atom 1s22s22p63s1
• Sodium ion 1s22s22p6 (Sodium atom lost 1 electron)
• Neon 1s22s22p6
• Sodium ion has the same electron configuration as neon
• Octet rule states that atoms gain, lose, or share electrons to acquire a full set of
___________________ valence electrons (to be like a noble gas)
Electronegativity
• Indicates an element’s ability to _________________________ electrons in a chemical bond
• fluorine (F) is the most electronegative element
• Cesium (Cs) and francium (Fr)are the least electronegative
• Noble gases do not tend to have an electronegativity number since they tend not to form
__________________
Trends with Electronegativity
• Electronegativity___________________________ as you move left-to-right across a period
• Electronegativity _____________________________ as you move down a group
9
Condensed Aufbau Diagram
Try
these:
1
s
2
s
2p
pp
2p
pp
2p
pp
3s
3p
3p
3p
4s
3d
3d
3d
3d
3d
Na:
Ca:
1
s
2
s
2p
pp
2p
pp
2p
pp
3s
3p
3p
3p
4s
3d
3d
3d
3d
3d
Mn:
1
s
2
s
2p
pp
2p
pp
2p
pp
3s
3p
3p
3p
4s
3d
3d
3d
3d
3d
Si:
1
s
2
s
2p
pp
2p
pp
2p
pp
3s
3p
3p
3p
4s
3d
3d
3d
3d
3d
F:
1
s
2
s
2p
pp
2p
pp
2p
pp
3s
3p
3p
3p
4s
3d
3d
3d
3d
3d
Ar:
1
s
2
s
2p
pp
2p
pp
2p
pp
3s
3p
3p
3p
4s
3d
3d
3d
3d
3d
Zn:
1
s
2
s
2p
pp
2p
pp
2p
pp
3s
3p
3p
3p
4s
3d
3d
3d
3d
3d
10