BIO160 Chapter 2.docx

6 Pages
Unlock Document

University of Mississippi
Biological Science
BISC 160
Dr.Beckie Symula

Chapter 2 The ratio in hair protein of the heavy isotope 1O to its lighter counterpart 1O reflects the ratios in local weather. 2.1 How does atomic structure explain the properties o-24atter?  Dalton: the mass of a proton, amu, 1.7x10 grams o An electron is .0005 daltons  An element consists of online one kind of atom o Stars have abundant amounts of hydrogen and helium o Earth’s crust are almost half oxygen, 28% silicon, 8% aluminum, 2-5% sodium, magnesium, potassium, calcium, and iron o 98% of the mass of every living organism is carbon, hydrogen, nitrogen, oxygen, phosphorus, and calcium  Each element has a different number of protons o Atomic number: the number of protons in an atom  does not change, unique to each element o Every element except for hydrogen has one or more neutrons in its nucleus.. o Mass number: total number of protons and neutrons  The number of neutrons differs among isotopes o Isotopes: have the same number of protons but different numbers of neutrons in that one element  Hydrogen(1 proton no neutrons)  Deuterium(1 proton 1 neutron)  Tritium (1 proton 2 neutrons) o Radioisotopes: unstable and spontaneously give off energy in the form of alpha, beta, or gamma radiation from the nucleus  Called “radioactive decay”  Radioisotopes are used to date fossils 60  Radiation from Co(Cobalt-60) kills cancer  The behavior of electrons determines chemical bonding and geometry o The behavior of electrons explain how chemical reactions occur o Orbital: the region of space where the electron is found at least 90 percent of the time  As we move from lighter to heavier atoms in the periodic chart, the orbitals are filled in a specific sequence, in a series of what are known as electron shells, or energy levels, around the nucleus  First shell: one orbital—s.  Second shell: four orbitals—s and 3p  S orbitals have the shape of a sphere while p orbitals are directed at right angles to one another(3D)  Additional shells: elements with 10 or higher electrons; farther a shell is from the nucleus, the higher the energy level is for an electron in that shell o Outermost shell = valence shell  Determines how the atom combines with other atoms  If all four orbitals are full the atom is stable(noble gases)  Atoms with unpaired electrons will undergo reactions to fill their outer shells  Reactive atoms can share or lose/gain electrons to become stable(bonds called molecules)  Rule of octet: tendency of atoms to become stable by filling outer shells with 8 electrons  Hydrogen is an exception because it attains stability with only 2 electrons 2.1 Summary: The living world is composed of the same set of chemical elements as the rest of the universe. An atom consists of a nucleus of protons and neutrons, and a characteristic configuration of electrons in orbitals around the nucleus. This structure determines the atom’s chemical properties. 2.2 How do atoms bond to form molecules?  Chemical bond: an attractive force that links two atoms together in a molecule  Covalent bonds: strong bonds that result from the sharing of electrons o Compound: a substance made up of molecules with two or elements bonded together in a fixed ratio o For a given pair of elements, the length of a covalent bond is the same o The spaces are evenly distributed (think of tetrahedral model) o Single, Double, and triple(rare) bonds. Triple is rare but N2. o Electronegativity: the attractive force that an atomic nucleus exerts on electrons in a covalent bond  Depends on how many positive charges(protons) a nucleus has, and on the distance between electrons in the bond and nucleus(closer=stronger)  If two atoms are close in electronegativity they will share electrons equally in a nonpolar covalent bond  When electrons are drawn to one nucleus more than to the other, it is called a polar covalent bond  Oxygen end of a hydrogen-oxygen bond has a slightly negative charge (δ-, delta negative) and the hydrogen end has a + slightly positive charge (δ , delta positive). This is called polar.  Ionic bonds: an atom gains or loses one or more electrons to achieve stability o Ions are electrically charged particles that form when atoms gain or lose one or more electrons.  Sodium ions (Na ) has a +1 charge because it has one electron les
More Less

Related notes for BISC 160

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.