Transcript CH2 Review
Chemistry Review ELEMENTS OF LIVING MATTER •OXYGEN •CARBON •HYDROGEN •NITROGEN There are other elements that are important also… IN INANIMALS: PLANTS: • • • • • • Potassium Sulfur Calcium Phosphorus Iron Sodium Helps maintain the fluid & electrolytes in the body. In some amino acids Component of bones & co-factor co-factor in in some some enzymes enzymes Phosphate groups in ATP In hemoglobin (haemoglobin) & in in cytochromes cytochromes In membrane functions & sending nerve impulses HELIUM ATOM NUCLEUS ELECTRONS NEUTRONS ORBITAL Proton # changed= new element Electron # changed= a charged ion Neutron # changed= an isotope PROTONS Some discussion questions • How many electrons 2 on the s orbital and 8 fit on in theeach next orbital? two p orbitals • How does proton to the They’re thethe same on an number element ifcompare it is electron number? unaltered/uncharged • What is the trend ofright electronegativity among Increases from left to across a row and decreases atoms? from top to bottom down a column Atoms do with you full outer shellsthe are more stable & of lesselectrons reactive; elements • How think number on the made of atoms with partially complete outer shells are more reactive; the outer orbital of each atom relates to how stable closer the atom is to having a completely full or completely empty outer the is? it reacts with other atoms. shell element the more violently • Which elements are VII the most reactive? The halogens; column Isotopes • Is an atom with more neutrons than “normal” – = greater mass • Isotopes can be stable such as C-13 or they can be unstable like C-14. – C-14 is a radioactive isotope • Its nucleus decays spontaneously, giving off particles of energy. • When the decay goes on long enough it will change the number of protons which will then change to a different element. • EX: C-14 will change to N. – What are some uses? • • • • Fossil dating Used as tracers Provide high quality imaging of organs & detecting tumors… Allow produce to have a longer shelf-life. Ionic Bonding • A strong bond • Opposite charge atoms bond & an electron is lost by one atom & gained by the other. – Cation: when the charge of an atom is positive • The atom lost an electron – Anion: when the charge of the atom is negative • The atom gained an electron Ionic Bonds Everyday tablesalt NaCl Crystal The formation of the ionic bond in table salt Which atoms are the anions & which are the cations? LiCl MgO Discussion Questions • Which elements ofVII thebecause periodic tend to become The atoms in column theytable are only missing one electron negative ions potentialneeded for gaining & they have the (greatest high electronegativity to stealan oneelectron)? from Why? another atom The elements to the to far left in column I, because they(have have low • Which ones tend become more positive the electronegativity have onlytheir 1 electron on their outer orbital weakest ability&to keep electrons)? Why? Columns I and VII, would columnscombine II and VI well in order for both to • Which columns be more stable? Columns I and VII, columns and VI table tend to make ionic • Which elements on the IIperiodic bonds? Atoms with high electronegativity are able to steal electrons most easily, Atatoms point an element is unable totend stealto enough give enough electrons in order to •some How electronegativity correlate with ionic bonding? withdoes low electronegativity have or their electrons stolen from them become stable because it does not have enough electronegativity to steal as many • Why don’t all the elements of the periodic table form ionic electrons as it needs or it has too much electronegativity to give away as many as would bonds? be necessary. • What do atoms that cannot form ionic bonds do to Form a covalent bond become more stable? Covalent Bonding VERY STRONG BOND HOW DOES THIS HAPPEN? WHY DOES THIS HAPPEN? Attraction of electrons to the protons The number of open places on the valence How do the valence electrons shell determines the number of bonds it influence can make. molecular bonding? A large difference between electronegativities of 2 atoms then the one w/higher electronegativity can steal How electrons from thedoes other. electronegativity If both are fairly equal then they molecular bonding? will form ainfluence covalent bond. HOW MANY BONDS CAN THE FOLLWING ATOMS MAKE? • HYDROGEN • OXYGEN • CARBON 1 2 4 POLAR vs NONPOLAR Polar= when one atom is bonded to another and the electronegativity is not the same causing the electron(s) of one atom to be shared unequally or the asymmetrical arrangement of the molecules Nonpolar= when there is an equal sharing of electrons between two different atoms or because of the symmetrical arrangement of polar bonds. HYDROGEN BONDING: DRAW 2-3 MOLECULES OF WATER & INDICATE THE HYDROGEN BONDS WEAK BONDS Not effective over long distances Formed by the attraction of opposite partial electric charges between two polar molecules Draw a hydrogen atom & fluorine atom (no need to worry about the neutrons & protons this time) WHICH ATOM WOULD BE CONSIDERED MORE ELECTRONEGATIVE? WHY? HOW CAN THESE ATOMS BECOME MORE STABLE? WHAT DO YOU CALL THIS?