Chapter 5 Electronic Struicture & Periodic Trends.notebook 1 October 17, 2014 Nov 217:22 AM Chapter 5: Electronic Structure & Periodic Trends The electromagnetic spectrum shows the arrangement of wavelengths of electromagnetic radiation, with the visible range from 700 to 400 nm. TrueFalse on the Electromagnetic Spectrum 1. Blue light has shorter wavelength than red light. 2. Xrays have lower frequencies than radio waves. 3. Microwaves have higher frequencies than gamma rays 4. Visible radiation composes the major portion of electromagnetic spectrum Electromagnetic Spectrum Nov 222:09 PM Wavelength ( ) – distance between two consecutive points in a wave (in m or nm) Frequency ( ) – number of waves (cycles) per second that pass a given point in space (in Hz) Speed (c) – speed of light (3×10 8 m/s) Wavelength Frequency Conversion Photosynthesis uses light with frequency of 4.54 x 10 14 Hz. What wavelength does this corresponds to? (in m, and nm) The wavelength of a microwave is 1.2 x 10 1 m. What is the frequency of this radiation?
The electromagnetic spectrum shows the arrangement of wavelengths of electromagnetic radiation, with the visible range from 700 to 400 nm.
TrueFalse on the Electromagnetic Spectrum1. Blue light has shorter wavelength than red light.2. Xrays have lower frequencies than radio waves.3. Microwaves have higher frequencies than gamma rays4. Visible radiation composes the major portion of electromagnetic spectrum
Electromagnetic Spectrum
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Wavelength ( ) – distance between two consecutive points in a wave (in m or nm)
Frequency ( ) – number of waves (cycles) per second that pass a given point in space (in Hz)
Speed (c) – speed of light (3×108 m/s)
Wavelength Frequency ConversionPhotosynthesis uses light with frequency of 4.54 x 1014 Hz. What wavelength does this corresponds to? (in m, and nm)
The wavelength of a microwave is 1.2 x 101 m. What is the frequency of this radiation?
Inverse relationship between wavelength and frequency and between wavelength and energy
Linear relationship between frequency and energy
Nov 222:09 PM
Elements Have a Unique Atomic SpectrumWhen light from an element that is heated passes through a prism, it separates into a unique set of distinct lines of color called an atomic spectrum.
Atomic Spectra and Energy Levels
Photons: photons are the fundamental particle of light.
All photons travel at the speed of light as a wave of energy.
Atomic Orbitals are mathematical descriptions of where the electrons are in an atom (or molecule) are most likely to be found.
Each orbital has a name. The orbital occupied by the hydrogen electron is called a 1s orbital. • The "1" represents the fact that the orbital is in the first energy level. • The "s" tells you about the shape of the orbital. "s" orbitals are spherically symmetric around the nucleus
Every energy level has an "S" orbital
Any orbital can only hold 2 electrons.
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p orbitals begin at the second energy level
At the first energy level, the only orbital available to electrons is the 1s orbital, but at the second level, as well as a 2s orbital, there are also orbitals called 2p orbitals.
At any one energy level there are three absolutely equivalent p orbitals. These are given the symbols px, py and pz.
At the third level, there is a set of five d orbitals as well as the 3s and 3p orbitals (3px, 3py, 3pz). At the third level there are a total of nine orbitals altogether.
At the fourth level, as well the 4s and 4p and 4d orbitals there are an additional seven f orbitals 16 orbitals in all.
s, p, d and f orbitals are then available at all higher energy levels as well.
Shorthand Electron ConfigurationTo simplify the writing of lengthy electron configurations, the symbol of a noble gas may be substituted for the appropriately filled shells and orbitals.
The arrangement of electrons in the orbitals of an atom.
Electron Configurations
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Pauli Exclusion Principle
The blue electrons are pairedThe red electrons are unpaired
Hund’s Rule – electrons will not pair in an orbital until all orbital of equal energy contain one electrons.
An orbital can hold a maximum of 2 electrons. They must spin in opposite directions, they are said to be paired.
The valence electrons • determine the chemical properties of the elements.• are the electrons in the outermost, highest energy level.• are related to the group number of the element.
Example: Phosphorus has 5 valence electrons.5 valence electrons
P Group 5A(15) 1s22s22p63s23p3
All the elements in a group have the same number ofvalence electrons.Example: Elements in Group 2A (2) have two (2) valence electrons.
Be 1s22s2
Mg 1s22s22p63s2
Ca [Ar]4s2 Sr [Kr]5s2
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Periodic Table and Valence Electrons
Identify the number of valence electrons for each of the following:1. O A. 4 B. 6 C. 82. Al A. 13 B. 3 C. 1 3. Cl A. 2 B. 5 C. 7
Identify the number of valence electrons for each of the following:1. 1s22s22p63s23p1
Atomic SizeAtomic size • is described using the atomic radius.• is the distance from the nucleus to the valence electrons.• increases going down a group.• decreases going across a period from left to right.
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Learning Check
2. Arrange the elements in order of increasing atomic radiusa. S, Cl, Al, Na b. Mg, Sr, F, B
c. Bi, Cs, Ba, I d. P, F, Ra, Cs
1. Which of the following has a greater atomic radius?
Metallic CharacterThe metallic character increases when an element can lose its valence electrons more easily, it• increases down a group where electrons are easier to remove.• decreases across the period because electrons are harder to remove.
