Chapter 4 Arrangement in Electrons in Atoms By Connor Campbell Lindsay Fisher Paul Gonzalez  Sonya McCormick Nick Solomon

Section 1: The Development of the New Atomic Model Properties of Light The Wave Description of Light Electromagnetic Radiation: a form of energy that exhibits wavelike behavior as it travels through space Electromagnetic Spectrum: formed by all of the electromagnetic radiations Other types of electromagnetic radiation include: X-rays, ultraviolet and infrared light, microwaves and radio waves

All forms of electromagnetic radiation move at a constant speed of 3 All forms of electromagnetic radiation move at a constant speed of 3.0 x 10^8 m/s Wavelength (λ): the distance between corresponding points on adjacent waves Frequency (v): the number of waves that pass a given point in a specific time, usually one second Expressed in waves/second Measured in hertz

Speed of Light Equation                                      C = λv speed of light = wavelength * frequency

The Photo Electric Effect Photoelectric Efficent: refers to the emission of electrons from a metal when light shines on the metal The Particle Description of Light Quantum: the minimum quantity of energy that can be lost or gained by an atom

E = hv energy = Planck’s constant * frequency Energy of a Wave: E = hv      energy = Planck’s constant * frequency  Planck’s constant (h) = 6.626 * 10^-34

Photon: A particle of electromagnetic radiation having zero mass and carrying a quantum of energy   Ephoton= hv In order for an electron to be ejected from a metal surface the electrons must be struck by a single photon possessing at least the minimum energy required to knock the electron loose Different metals are bound more or less tightly therefore different metals require different minimum frequencies

 The Hydrogen-Atom Line-Emission Spectrum Ground State: the lowest energy state of an atom Excited State: a state in which an atom has a higher potential energy than it its ground state

When an excited atom returns to its ground state, it gives off the energy it gained in the form of electromagnetic radiation When a narrow beam of the emitted light was shined through a prism, it was separated into a series of specific frequencies (and therefore specific wavelengths, λ=c/v) of visible light

Line-Emission Spectrum: the band of light produced from emitted light being shown into a prism Continuous Spectrum: the emission of a continuous range of frequencies of electromagnetic radiation  Attempts at explaining why hydrogen atoms give off only specific frequencies of light is known as the quantum theory The energy of the photon emitted from an excited electron going back to ground state is (Ephoton = hv) is qual to the difference in energy between the atom’s initial state and its final state

Atomic Orbitals and Quantum Numbers Schrödinger Equation: Specifies the properties of an electron. Quantum Numbers: Show the properties of atomic orbitals and the electrons in those orbitals.

Principal Quantum Number Symbolized by n, and represents an electron’s main energy level. Only has positive integer values. The higher the principal quantum number is, the more energy the electron has, and the farther away from the nucleus it is. The number of sub-orbitals in an electron shell is equal to n2.

Angular Momentum Quantum Number All electron shells, except the first, have sub-levels that exist as differently shaped orbitals. Symbolized by l. Can have a value of 0, or be less than n-1. Values of l correspond to different orbital shapes.

Angular Momentum Quantum Number (cont.) Orbital Shape s 1 p 2 d 3 f s orbital is spherical p orbital is shaped like a dumbbell d orbital is shaped like a flower, or two intersecting p orbitals

Magnetic Quantum Number Represented by m. Shows the orientation of the different orbitals. s orbitals, as spheres, only have one orientation. Other orbitals can be oriented on one of 3 different axises, x, y, or z.

Spin Quantum Number Has a value of either +1/2 or -1/2 Shows the direction an electron spins about its internal axis Each orbital can hold two electrons spinning in opposite directions.

Rules Governing Electron Configuation electron configuration- the arrangement of electrons in an atom  Aufbau principle- an electron always occupies the lowest energy orbital that can receive it  Paulie exclusion principle- no two electrons in the same atom can have the sam four quantum numbers  Hund's rule- orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron, and all electrons in singly occupied orbitals must have the same spin state  

Representing Electron Configurations Orbital Notation each orbital is represented by at least one line the orbital can have at most two electrons per line, with the first one pointing up and the second one pointing down for example, 1s is written under the line representing the first orbital

Electron Configuration Notation no lines level number, orbital letter, superscript for number of electrons for example, 1s2 this means that there are 2 electrons in the s orbital of the first level

Elements of the 2nd Period highest occupied number- the electron-containing main energy level with the highest principal quantum number inner-shell electrons- electrons that are not in the highest occupied energy level 2nd period elements have electrons that occupy the the second energy level 

Elements of the 3rd Period noble gases- group 18 elements noble gas configuration- an outer main energy level fully occupied, in most cases, by 8 electrons all elements in the 3rd period and below can be written in noble-gas notation write the name of the noble-gas in the period before in brackets write the element's remaining electrons in electron configuration notation ex.: Na is [Ne]3s1

Elements of the 4th Period The elements in the fourth period are the first elements to include the d-orbital in their electron configuration. The noble-gas notation of elements of the fourth period is done with the following steps. 1. Argon in brackets symbolizing 3s^2 3p^6. 2. The 4s orbital, followed by the 3d orbital, then the 4p orbital. There are some elements in the fourth period that don't follow Hund's rule in their electron configuration such as;  Chromium 4s^1 3d^5.

Elements of the Fifth Period The elements of the fifth period follow the electron configuration of the fourth period, however instead of 4s,3d, and 4p, it is 5s, 4d, and 5p. There are some elements that don't follow the expected electron configuration, when the configuration has the lowest possible energy.

Elements of the 6th and 7th Periods The 6th period is the largest period out of any of the preceding periods, containing 32 elements. The elements of the 6th period have an f orbital, containing up to 14 electrons. The noble-gas notation would be; 1. Xenon in brackets symbolizing 6s^2 5d^1 4f^1 Then the 4f orbital, the 5d orbital, and finally the 6p orbital.  The 7th period is incomplete and is mostly synthetic elements.