Introduction to Chemical Bonding Chemical Reactions During chemical

Introduction to Chemical Bonding

Chemical Reactions: • During chemical reactions, elements combine, rearrange, or break apart with others to form new substances. • New substances are created when chemical bonds are broken or created. New Substance Original Substance Chemical Reaction Magnesium Metal http: //www. polmag. pl/en/media/magnesium. jpg http: //www. bcscience. com/images/m agnesium_burn. jpg Magnesium Oxide http: //jchemed. chem. wisc. edu/JCESOFT/CCA/CC 3/STILLS/MAGAIR/64 JPG 48/6. JPG

Evidence of Chemical Reactions: Fire/Burning Color change without dye New gas created Heat released Heat absorbed : //en. wikipedia. org/wiki/Self-heating_can tp: //static. howstuffworks. com/gif/coldpack. jpg • • • http: //amazingrust. com/Experiments /background_knowledge/Images/Fir e-big. jpg http: //z. about. com/d/chemistry/1 /G/5/a/demonstration. jpg http: //www. uncp. edu/home/mcclurem/pta

Compounds are more than one kind of element joined together. Octet Rule: Describes how chemical bonds happen. • Atoms want a full valence (or outer electron energy level). • Full valence will mean having 8 valence electrons. http: //www. chemprofessor. com/periodicqm_files/image 005. gif

Why are these atoms negative? Octet Rule … Gaining electrons (and electrons • are Tonegative) reach means full valence, some atoms “want” more It is easier for the to atom to to lose electrons and others “want” gain negative charge than positive gain 1, 2 or 3 electrons rather charges (protons). electrons. than losing 5, 6 or 7. – Atoms with FEWER than 4 valence electrons will bond by losing those electrons. • These atoms will become positively charged! – Atoms with MORE than valence electrons It is 4 easier for the atom to lose 1, 2 or 3(up electrons rather will bond by gaining electrons to eight). Why are these atoms positive? than gaining 5, charged! 6 or 7. • These atoms will become negatively Losing electrons (and electrons –are Atoms withmeans 4 valence electrons can gain or negative) lose electrons. It depends on the element to more protons (positive charge) which it ischarges. bonding. than negative

Example: Sodium (Na) • Valence? 1 • Easiest way to follow Octet Rule? Lose 1 electron • If following Octet Rule, what’s the charge? +1 http: //www. historyforkids. org/scienceforkids/chemistry/atoms/ pictures/sodium. jpg A chemical bond is created by the sharing or exchange of electrons between elements.

Example: Fluorine (F) • Valence? 7 • Easiest way to follow Octet Rule? Gain 1 electron • If following the Octet Rule, what’s the charge? – 1 http: //www. bbc. co. uk/schools/gcsebitesi ze/science/images/diag_fluorine. gif

What will happen if Sodium and Fluorine atoms are mixed? • Electrons could transfer between the atoms. • A sodium atom could lose an electron to a fluorine atom. • Both atoms are left with full valence & are bonded together, creating a compound.