1. Aim: How to distinguish an atom in the ground state and the excited state? DO NOW: Identify
Green = proton
Blue= neutron
Red= electron
Which element is this? How can we tell?
How many electrons are in the first shell? Second shell?

2. Atomic Orbitals
An atomic orbital is thought of as the most probable location of an electon
Each shell in an atom is subdivided into orbitals. Electrons are found in the orbitals.
)1 )2 )3)4
nucleus

3. Electrons and Electron Shells(Energy Levels)
When electrons are arranged in an atom, the innermost shell is filled first and then the outer shells are filled
Each shell can hold a certain amount of electrons
The number of electrons in a shell cannot surpass the shell’s capacity
Energy Level/Shell
Total Electrons per Level 1 2 8 3 18 4 32

4. Electron Configuration
Electron configuration is a condensed way of representing the pattern of electrons in an atom.
For oxygen: 2-6
(2 electrons in first shell, 6 in second shell)

5. Electronic Structure Element Bohr Structure Electron Configuration
Electrons
Periodic Table Group
Fluorine (F)
2-7
2 e- in 1st shell
7 e- in 2nd shell 17
Neon (Ne)
2-8
2e- in 1st shell
8 e- in 2nd shell 18
Sodium (Na)
2-8-1
1 e- in 3rd shell 1
Calcium (Ca)
8 e- in 3rd shell
2 e- in 4th shell 2

6. Ground State
An atom in the ground state is defined as electrons being in the lowest energy electron configuration
The electron configuration as written in the periodic stable shows the electrons in their ground state

7. Energy and Electrons
Electrons further away from the nucleus have more energy than electrons closer to nucleus
Ex: For the aluminum atom, the two electrons in the first shell have less energy than the 3 electrons in the 3rd shell
Discussion: Electrons can move throughout the electrons cloud from one shell to another shell. In terms of electrons absorbing or releasing energy, how do you think an electron in the 2nd shell can jump to the 3rd shell?

8. Excited State
Electrons can move to a higher energy level (shell) without filling the lower energy level first
electrons do this by absorbing energy
An excited state is an energy state of higher energy
Excited electrons fall back to the ground state by releasing energy in the form of light
Energy released are small, specific amounts of energy

9. Note
When atom becomes excited, the electrons jump to a higher energy level; HOWEVER, the OVERALL number of electrons does not change

14. Explain in terms of electrons and energy how an atom can go from
ground to excited state
Excited to ground state

15. Draw Bohr Diagram for Aluminum atom in the Ground State and the Excited State On the arrows, write if energy is absorbed or released by the atom

16. Sample Questions Examples Fluorine. How many protons? Electrons?
Ground state e- config (Periodic Table)
2-7
Working with your partner write 2 possible excited state e- configs
1-7-1
2-6-1
1-8
Note how an inner level is left partially filled b/c an e- has jumped to a higher energy level Note that TOTAL # OF e- REMAINS THE SAME! 

17. Regent Questions
The Bohr model of the atom was developed in the early part of the twentieth century. A diagram of the Bohr model for one atom, in the ground state, of a specific element is shown below. The nucleus of this atom contains 4 protons and 5 neutrons
State the atomic number and the mass number of this element.
State the number of electrons in each shell in this atom in the ground state.
Using the Bohr model, describe the changes in electron energy and electron location when an atom changes from the ground state to an excited state.