Name:______Date:______

KeyChapter 5 Electrons in Atoms

Electron Review Guide

  1. Label the following on the periodic table: s block, p block, d block, f block, and the energy levels.

  1. Why are electrons important? In other words, what are electrons responsible for?

Electrons are important because they determine the properties of elements. The electrons also are involved in bonding.

  1. Write the electron configuration for the following elements:
  1. Calcium:_1s22s22p63s23p64s2______
  2. Ca+2:_1s22s22p63s23p6 (lost 2 electrons)______
  3. Chlorine:_1s22s22p63s23p5______
  4. Selenium:_1s22s22p63s23p64s23d104p4______
  5. Se-2:_1s22s22p63s23p64s23d104p6 (gained 2 electrons)______
  6. Cesium:_1s22s22p63s23p64s23d104p65s24d105p66s1______
  7. Nickel:_1s22s22p63s23p64s23d8______
  1. Determine the element from the following electron configurations:
  2. 1s22s22p63s23p64s23d104p2:__Ge______
  3. 1s22s22p63s23p64s23d104p65s24d105p66s24f8:__Tb______
  4. 1s22s22p63s23p64s23d5:_Mn______
  5. [Xe]6s2:___Ba______
  6. 1s22s22p63s23p64s23d104p65s24d105p6___Xe______
  7. What do each of the parts of the electron configuration stand for: 1s2?
  8. 1 represents the ___energy level______
  9. s represents the ___sublevel______
  10. 2 represents the ___number of electrons______
  11. Write the outermost energy level of nitrogen in its ground state.

2s22p3

  1. Describe how electrons go from ground state to the excited state and back down to ground state.

Electrons absorb energy and go from the stable ground state to the unstable excited state. The electrons emit energy in the form of light in order to return to the ground state.

  1. What is the Pauli Exclusion Principle? What is the Aufbau Principle? What is Hund’s Rule?

Pauli: electrons paired in an orbital must have opposite spin (one pointing up, one pointing down)

Aufbau: fill from the lowest energy levels first…i.e., go in order of 1s22s22p6 etc

Hund: All orbitals in a sublevel must have one electron before pairing electrons and all single electrons must have the same spin.

Excited State!

Below is an orbital diagram for an element in the excited state.

1.What element is it if it is neutral? __carbon (there are 6 total electrons, and in neutral atoms the #p=#e)______

2.How can you tell this atom is in the excited state?

The Aufbau Principle is broken. There is one electron in the 2s orbital and the other electron moved to a further energy level.

Write the Shorthand Configuration for the following elements:

  1. Sodium (Na):__[Ne]3s1______
  2. Iodine (I):__[Kr]5s24d105p5______
  3. Iron (Fe):__[Ar]4s23d6______
  4. Aluminum (Al):_[Ne]3s23p1______

Physics and the quantum Mechanical Model

  1. Look at the following equation. Write down what each variable represents and the units. If it is a constant, write down its numerical value. Write down the other two ways to write this equation.

c: _speed of light (3.0x108 m/s)______c=λν

λ:_wavelength (meters)______

ν:_frequency (Hz, 1/s, or s-1)______

ν= _cλ= __c__

λ ν

  1. Calculate the frequency of a wave that has a wavelength equal to 7.20x10-7 m.

ν=__c__

λ

ν= 3.0x108 m/s

7.20x10-7m

ν=4.7x1014 Hz

  1. Calculate the wavelength of a wave that has a frequency equal to 540x1012 Hz.

λ= __c__

ν

λ=3.0x108 m/s

540x1012 Hz

λ=5.56x10-7 m

  1. What is the relationship between frequency and wavelength?

The relationship between frequency and wavelength is an inverse relationship—as one increases the other decreases.

  1. HOW DO FIREWORKS WORK? WHY DO WE SEE DIFFERENT COLORS? Be sure to discuss frequency, energy, and wavelength along with what happens to the electron with respect to ground state and excited state.

An energy source is applied to a chemical and the electrons are bombarded by photons and absorb the energy. The absorbed energy allows the electron to break the attractive force between the electrons and the nucleus and the electron moves to an outer energy orbitals, which is called the excited state. The excited state is unstable, so the electron releases the absorbed energy in the form of visible light. We see different colors due to different spacings of orbtials in an element because the energy released depends on the fall back to ground state. The more energy, the shorter the wavelength so you see colors of shorter wavelength and vise versa.

  1. What are atomic emission spectra and why are they important?

Atomic emission spectra are color lines emitted by an element as it returns to the ground state. Each element has its own unique set of spectral lines, so we can use spectra to identify an element.

Another equation you need to know is E=hν

  1. What do the variables represent? What are their units?
  2. E=__energy (J )______
  3. h=_6.63x10-34 Js______
  4. What is the name of this constant?_Planck’s constant______
  5. ν=___frequency (Hz, 1/s, or s-1)______
  6. Calculate the energy of a wave with a frequency equal to 740x1012 Hz.

E=hν

E= (6.63x10-34 Js)(740x1012 Hz)

E=4.91x10-19 J

  1. Calculate the frequency of a wave with energy equal 5.678x10-21 J.

E=hν

ν= __E__

h

ν=5.678x10-21 J

6.63x10-34 Js

ν=8.56x1012 Hz