Electrons in Atoms Unit Bohr Model, Lewis Dot for Elements, Valence Electrons

Like our solar system … Nucleus is like our sun Electrons are like our planets Electrons on energy levels! Ask what is our nucleus made up of? Then click for nucleus picture Go to electrons are like planets Then say where do our electrons live at in our atom? The energy levels (click for the rest of the Bohr Model)

How do we draw a Bohr Model? Model Only Really works for Hydrogen How do we draw a Bohr Model? 1.) Draw a nucleus 2.) Determine how many electrons you need 3.) Draw energy levels around nucleus Each energy level can only hold so many electrons 1st = 2 e- 2nd = 8 e- 3rd = 8 e- 4th and up = 2 e- 4.) Place electrons on each energy level until you reach the amount of electrons you need (refer to step #2) How many e- on 1st = ____ 2nd = ____ 3rd = ____ 4th = ____ Total = ____ Ca 20 40.078

Draw the Bohr Model for: Sodium Oxygen 1.) Draw a nucleus 2.) Determine how many electrons you need 3.) Draw energy levels around nucleus Each energy level can only hold so many electrons 1st = 2 e- 2nd = 8 e- 3rd = 8 e- 4th and up = 2 e- 4.) Place electrons on each energy level until you reach the amount of electrons you need (#2) Draw the Bohr Model for: Sodium Oxygen

Identify the element from its Bohr Model How many e- on 1st = ____ 2nd = ____ 3rd = ____ 4th = ____ Total = ____ Proton Neutron Electron

Identify the element from its Bohr Model How many e- on 1st = ____ 2nd = ____ 3rd = ____ 4th = ____ Total = ____ Proton Neutron Electron

Valence Electrons The outermost electrons on the highest occupied energy level of an element

How do we find the number of valence electrons? Bohr diagram Periodic table BEST CHEAT SHEET EVER! + - How many valence electrons are present in the last energy level of Calcium?

1 2 3 4 5 6 7 8

How many valence electrons are in . . . Cl __________ Ba __________ Ne __________ He __________

X • • • • • • • • Lewis Dot Structures System of arranging dots to represent the valence electrons G. N. Lewis developed this system Dots represent the valence electrons Max of 8 around the symbol First two together Rest go “counter-clockwise” • • X • • • • • •

Example: How many valence electrons does phosphorous have? Write the Lewis dot structure for phosphorous

Practice Mg S Cl Rb Si Ar

IONS – charged atom Elements will gain or lose electrons to achieve an OCTET. This means they want to have 8 valence electrons Known as the OCTET RULE

Cation – K becomes K+ B becomes B3+ Positive ion Loses electrons to become more positive Why? Easier to lose 1, 2 or 3 e- than it is to gain 5, 6 or 7 e- K becomes K+ B becomes B3+

Anion Cl becomes Cl- O becomes O2- Negative ion Gains electrons to become more negative Why? Easier to gain 1, 2 or 3 electrons than to lose 5, 6, or 7 e- Cl becomes Cl- O becomes O2-

Draw the Lewis Dot Structure for these ions: Na+ O2- Mg2+

Draw the Lewis Dot Structure for these ions: Cl- Al3+ F-