ESSENTIAL QUESTIONS Why are some elements so stable, but others so reactive? What does an atom’s place on the Periodic Table tell chemists? . How why do atoms form chemical bonds? 1

By the end of this video you will be able to… Determine the # of valence e- for any element Draw the e- configuration (Bohr model) for any simple element based on position on PT Draw the e- dot structure for any element Draw covalent bonds (single, double, and triple) for any simple molecule 2

The Periodic Table Rare Earth Metals Noble Gases Alkaline Earth Metals Alkali Metals Halogens Transition Metals Rare Earth Metals 3

The Periodic Table p+ groups periods The periodic table is arranged in order of increasing number of _______. The periodic table is arranged into __________ (columns) and __________ (rows). p+ groups periods 4

Orbit vs. Orbital 2 e- in the 1st energy level 3 4 5 6 7 8 2 e- in the 1st energy level 2 e- in the 1st energy level 8 e- in the 2nd energy level 8 e- in the 2nd energy level 5

Electron Configuration Find these elements on the Periodic Table, what do they have in common? What do you notice about their electron configurations? 6

Valence Electrons valence group p+ valence e- reactivity The electrons in the outermost energy level of an atom are called the _______________ electrons. The number of valence electrons for an element is equal to the _____________ (column) number. While the periodic table is ordered by the number of ______, the actual shape of the table comes from the number of ______________ ______. The #of valence e- determines the _____________ of elements. valence group p+ valence e- reactivity 7

e- configuration The atom shown on the right is the e- configuration of which element? Oxygen Thallium Sulfur Selenium 8

Valence electrons Which element is in the 4th energy level and has 2 valence electrons? Carbon Calcium Strontium Magnesium 10

Which element is in the 4th energy level and has 2 valence electrons? Calcium 20 p+ 20 n0 20 e-

e- Configuration 8 p+ 8 n0 8 e- 10 p+ 10 n0 10 e-

e- Dot Structure core electrons valence electrons e- dot structures Electrons in the inner orbitals of atoms are called _____ ___________ . However, to understand the reactivity of elements, chemists are mostly concerned with the electrons in the outermost energy level called the __________ _____________ . In order to simplify drawing the valence electrons, chemists use ___ _____ _____________ . Let’s try some examples! core electrons valence electrons e- dot structures

Periodic Trend – Valence e-

e- Dot Structure

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10 9 8 7 6 5 4 3 2 1 11/6 Electron Configuration How many protons does Chlorine have? How many neutrons does Chlorine have? Write the atomic notation for Chlorine. What is the name of the periodic table family for Chlorine? What energy level is Chlorine in? What does that tell you? What group is Chlorine in? What does that tell you? Draw the full electron configuration for Chlorine ? Draw the e- dot structure of Chlorine. A Chlorine atom is dangerously reactive, why do you think this is when it’s neighbor Argon is UNreactive?

Covalent Bonding stable 8 octet rule noble gas non-metal share octet Atoms are actually most _________ when they have a full set or usually _____ valence e-. This tendency for atoms to be stable with eight valence electrons is called the ________ ______. The only group of elements that naturally satisfies the octet rule is the ________ ______ family. In order to achieve a stable valence shell of 8 e-, ______________ atoms can ________ electrons to achieve an __________ . Atoms may share 1, 2, or 3 pairs of e-to make __________ , __________ , or ________ connections called ______________ __________ . These bonds hold the _______________ together because the ____________ charged nuclei are ____________ to each other’s __________ ___ charged _____________ __________. 8 octet rule noble gas non-metal share octet single double triple covalent bonds molecule positively attracted negatively electron clouds

Covalent Bonding

Covalent Bonding

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Octet Rule Which of the following obeys the octet rule an d is the correct structure of N2? A B C Too many e- each N only has 5 valence e- Not an octet, only 6 e- around each Nitrogen Correct  10 e- total and 8 e- around each Nitrogen

A B C Octet Rule C O C O C O Draw the covalent bonding in CO. Which of the following is the correct structure of CO? Explain why the other two answers are incorrect. C O C O C O A B C