BUILDING ATOMS

REVIEW ATOMIC CONCEPTS BUILD MODELS OF ATOMS AS A REVIEW BUILD MODELS OF IONIC BONDING BUILD MODELS OF COVALENT BONDING BUILD MODELS OF HYDROGEN BONDS COMPARE & CONTRAST IONIC, COVALENT AND HYDROGEN BONDING OBJECTIVES

BUILD A HELIUM ATOM  Draw the helium atom & label its parts

Jot down the following  What would happen if the number of protons changed?  What would happen if the number of electrons changed?  What would happen if the number of neutrons changed?

BUILD A HYDROGEN ATOM  Draw the hydrogen atom & label its parts  What happens if you change the number of:  Protons?  Electrons?  Neutrons?

ORBITALS

BUILD ATOMS CNOFCNOF

ELECTRONEGATIVITY  "Electronegativity is the power of an atom when in a molecule to attract electrons to itself."  Increases left to right  Decreases top to bottom

QUESTIONS  How many electrons fit on each orbital?  How does the proton number compare to the electron number?  How does the number of electrons in the outer orbital relate to the stability of the element?  Which elements are the most stable? Why?  Which elements are the most reactive? Why?

QUESTIONS  How many electrons fit on each orbital?  2 on the inner s orbital  Eight on the next two

QUESTIONS  How does the proton number compare to the electron number?  They are the same if the element is unchanged/unaltered

QUESTIONS  How does the number of electrons in the outer orbital relate to the stability of the element?  Elements with full orbitals or valence shells are more stable & less reactive  Elements with partially complete valence shells are more reactive The closer an element is to having a completely full or completely empty valence shell is more reactive

QUESTIONS  Which elements are the most stable? Why?  Nobel gases (Column VIII)  Their outer orbitals are filled

QUESTIONS  Which elements are the most reactive? Why?  The halogens (VII) Their outer shell is almost complete  Metals (I) Their outer shell is almost empty (need to lose one electron)

BUILD A FLUORINE ATOM & A HYDROGEN ATOM  HOW WILL THE GAIN/LOSS OF AN ELECTRON CHANGE THE STABILITY OF EACH?  WHAT HAPPENS WHEN AN ELECTRON IS MOVED FROM HYDROGEN TO FLUORINE?  MOVE THE ELECTRONS  DRAW A BEFORE AND AFTER DIAGRAM OF THE HF MOLECULE

BUILD IONIC COMPOUNDS  LiCl  MgO  BeS  NaF

IONIC BONDING  Ionic bonding is the complete transfer of valence electron(s) between atoms.  It is a type of chemical bond that generates two oppositely charged ions.  In ionic bonds, the metal loses electrons to become a positively charged cation, whereas the non-metal accepts those electrons to become a negatively charged anion.  Ionic bonds require an electron donor, metal, and an electron acceptor, nonmetal.

QUESTIONS  In the models you built, which atoms are the cations? Which are the anions?  Which elements of the periodic table tend to become negative ions/anions (have the greatest potential for gaining electrons)? Why?  Which elements of the periodic table tend to become positive ions/cations (have the weakest ability to retain their electrons)? Why?  Which columns would combine well in order for both to be more stable?

QUESTIONS  Which elements of the periodic table tend to make ionic bonds?  How does electronegativity correlate with ionic bonding?  Why don’t all the elements of the periodic table form ionic bonds?  What do atoms that cannot form ionic bonds do to become more stable?

QUESTIONS  In the models you built, which atoms are the cations? Which are the anions?  Cations – Li, Mg, Be, Na  Anions – Cl, O, S, F

QUESTIONS  Which elements of the periodic table tend to become negative ions/anions (have the greatest potential for gaining electrons)? Why?  Column VII (halogens)  Only missing one electron & have high electronegativity

QUESTIONS  Which elements of the periodic table tend to become positive ions/cations (have the weakest ability to retain their electrons)? Why?  Far left, column I  They have only one electron in their outer orbital & have low electronegativity

QUESTIONS  Which columns would combine well in order for both to be more stable?  Columns I & VII  Columns 2 & VI

QUESTIONS  Which elements of the periodic table tend to make ionic bonds?  Columns I & VII  Columns II & VI

QUESTIONS  How does electronegativity correlate with ionic bonding?  Atoms with high electronegativity steal electrons  Atoms with low electronegativity have their electrons stolen

QUESTIONS  Why don’t all the elements of the periodic table form ionic bonds?  Elements are unable to steal or give enough electrons Electronegativity too low to steal enough electrons Electronegativity too high to release enough electrons

QUESTIONS  What do atoms that cannot form ionic bonds do to become more stable?  They share

BUILDING COVALENT MOLECULES  Make two hydrogen atoms  Are these atoms likely to form ionic bonds? NO – have equal electronegativity & cannot give or take  What can these atoms do to become stable? Form covalent bonds

BUILD COVALENT MOLECULES H2H2

 CH 4  NH 3

BUILD COVALENT MOLECULES  O 2  CO 2

COVALENT BONDING  Electrons are shared – valence shells then complete

BUILD COVALENT MOLECULES C2H6C3H8C2H6C3H8

C2H6C3H8C2H6C3H8

 C 2 H 6 (ethane)  C 3 H 8 (propane)

QUESTIONS  How do the valence electrons influence molecular bonding?  How does electronegativity influence molecular bonding?

QUESTIONS  How do the valence electrons influence molecular bonding?  The number of open places on the valence shell determine the number of bonds the atom can form

QUESTIONS  How does electronegativity influence molecular bonding?  If the difference in electronegativity between the 2 atoms is great, then ionic bonds form (one atom steals the atoms from another)  If the electronegativity is equal (or close), then covalent bonds form

HYDROGEN BONDING - DRAW  CH 4  C 2 H 6  C 3 H 8

HYDROGEN BONDING - DRAW  O 2  CO 2

HYDROGEN BONDS  How many bonds can the following atoms make:  H?  O?  C?

HYDROGEN BONDING - DRAW  H 2 O  H 2  O 2  CH 2 F  CH 4

QUESTIONS  Which molecules are symmetrical?  Which are polar and which are non-polar?  How does symmetry correlate with polarity?  How does electronegativity correlate with polarity?

QUESTIONS  Which molecules are symmetrical?  H 2, O 2, CH 4

QUESTIONS  Which are polar and which are non-polar?  Polar - H 2 O & CH 2 F  Non-polar - H 2, O 2, CH 4

QUESTIONS  How does symmetry correlate with polarity?  Symmetrical molecules are non-polar  Asymmetrical molecules are polar

QUESTIONS  How does electronegativity correlate with polarity?  The atom in the molecule with the higher electronegativity will pull the electrons to it unequally  This creates an unequal distribution of charge (without becoming a charged ion)

HYDROGEN BONDING  Bonds that forms between the positive and negative ends of a water molecule (hydrogen to oxygen)