Aim: How to distinguish an atom in the ground state and the excited state? 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. 1. State the atomic number and the mass number of this element. 2. State the number of electrons in each shell in this atom.

Review Electron Electrons are found in the electron cloud Negative charge In a neutral atom the # of protons = the # electrons The electron cloud has very little mass (low density, large volume); therefore, the atom is considered to be primarily empty space

Review of Electron Cloud Model (Wave Mechanical Model) In the wave-mechanical model (electron cloud model), the electrons are in orbitals, which are defined as the regions of the most probable electron location

Atomic Orbitals An atomic orbital is thought of as the region of space in which there is a high probability of finding an electron )1 )2 )3 )4 nucleus

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)

Ground State Lowest energy electron configuration As shown in the periodic table Innermost shell is filled first and then the outer shells are fills

Bohr Diagram Draw the Bohr of the Aluminum atom in the ground state.

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. How do you think an electron in the 2nd shell can jump to the 3rd shell?

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 Energy released are small, specific amounts of energy

Draw Bohr Diagram for Aluminum in the Excited State

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! 

U DO IT NOW! For the following configuration: 2-8-18-6 a) Identify the element. b) Propose an excited state. Simply add the electrons, which equal protons in a neutral atom, the atomic number. 2-8-18-6: 2+8+18+6 = 34 electrons indicates an atomic number of 34, which is Se Write a configuration with the same number of electrons as the ground state , but with a different configuration. 2-8-18-6(ground): 2-8-17-7 (excited) ♫NOTE – electrons furthest from the nucleus are most likely to be excited (promoted).