Wake-up

a. Refer to element below. Name the element.b. How many protons, neutrons, and

electrons?c. Naturally occurring Europium consists of

two isotopes with a mass of 160 and 161. If Eu-160 has abundance 49% and Eu-161 has 145%. What is the average atomic mass of Eu?

Electron Configuration … Where are electrons found?

Electrons are important…Because they feel each other first when atoms meet

.

Outer electrons of atoms interact with other electrons first!

Neils Bohr: 1913• Electrons move in orbitals around nucleus• AKA Planetary Model• Each orbital holds a certain number of electrons

with increasing energy

Electron Energy Levels1st Energy Level (surrounding the nucleus) contains

2 electrons

2 electrons

Electron Energy Levels2nd Energy Level (surrounding the nucleus)

contains 8 electrons

8 electrons

Electron Energy Levels3rd Energy Level (surrounding the nucleus)

contains 18 electrons• BUT if not enough to fill 18 and enough to fill 8,

fill 8 and move to next energy level.

18 electrons (8e-)

Electron Energy Levels4th Energy Level (surrounding the nucleus)

contains 32 electrons

32 electrons

How to Complete a Bohr Ring ModelFind the number of electrons; start filling the

energy levels starting with the 1st and working way out

Example #1: SodiumHow many electrons does Sodium have?

11

Potassium

Hydrogen

Carbon

Neon

Calcium