Ch. 8 Quiz
8.26 Define atomic radius. For main group elements, give observed trends as you a) move across period b) move down column
1. consider the stance between nonbonding atoms in a molecules or atoms that are touching each other but not bonded •determined this way called nonbonding atomic radius or Van Der Waals radius •represents radius of atom when it is not bonded to another atoms 2. define size, called bonding an atomic radius or covalent radius, defined diff for nonmetals and metals •Nonmetals: one half distance between two of atoms bonded together •Metal: one half distance between two atoms next to each other in a crystal of the •more generally, atomic radius refers to set of average bonding radii determined from measurements on a large number of elements and compounds. •atomic radius represents the radius when atom bonded to another atom and is always smaller than the van der waals radius a) move right across period, radius decreases b) move down column, radius increases
8.25 List number of valence electrons for each family in the periodic table, and explain relationship between number of valence electrons and resulting chemistry of the elements in the family a. alkali metals b. alkaline earth metals c. halogens d. oxygen family
A. Alkali Metals (group 1A) •one valence, most reactive metals •outer configuration is ns1, one electron beyond noble gas •react to lose ns1, obtaining noble gas configuration •tend to form 1+ cations B. Alkaline Earth Metals (group 2A) •two valence •outer configuration ns2, tend to be reactive •lose ns2 to form 2+ cations C. Halogens (group 7A) •seven valence •outer configuration ns2np5 •most reactive nonmetals •one electron away from noble gas config, and gain one electron to form 1- anions D. Oxygen Family (group 6A) •six valence, outer config ns2np4 •two short of noble gas, react to gain 2 e forming 2- anions
8.8 What is Coulomb's Law? Explain how potential energy of two charged particles depends on the distance between the charged particles and the magnitude and sign of those charges.
•Coulomb's Law: Potential energy (E) of two charged particles depends on their charges (q1 and q2) and separation (r). E=(1/4piE0)(q1q2/r) •PE positive for charges of same sign •PE negative for charges of opposite sign •Magnitude of PE depends inversely on separation between charged particles
8.14 What are degenerate orbitals? According to Hund's rule, how are degenerate orbitals occupied?
•Degenerate orbitals: orbitals of same energy •in multielectron atom, orbitals in a sublevel are degenerate •Hund's rule: when filling degenerate orbitals, electrons fill them singly first with parallel spins •result of an atom's tendency to find the lowest energy state possible
8.23 Explain how to write the electron configuration for an element based on its position in the periodic table
•Find the noble gas that precedes the element •inner electron configuration of that noble gas •place symbol for noble gas in [ ] •Obtain outer electron configuration by tracing element across the period and assigning electrons in the appropriate orbital
8.13 Why is electron spin important when writing electron configurations? Explain in terms of the Pauli exclusion principle.
•Pauli exclusion principle: no two electrons in an atom can have the same four quantum numbers. •two electrons in same orbital have three identical quantum numbers (n, l, ml), they must have different spin •Pauli exclusion principle implies each orbital has a max of two electrons with opposing spins
8.1 What are periodic properties?
•Periodic Property: property predictable based on the element's position within the periodic table
8.6 What observations led to the periodic law? What theory explains the underlying reasons for the periodic law?
•based on the observations that properties of elements recur and certain elements have similar properties •explains existence of periodic law is quantum-mechanical theory
8.24 Explain the relationship between the properties of an element and the number of valence electrons it contains
•chemical properties largely determined by the number of valence electrons •properties are periodic bc number of valence electrons is periodic •elements within a column in the periodic table have same number of valence electrons, also have similar chemical properties
8.12 What is an orbital diagram? Provide an example.
•different way to show electron configuration •symbolizes electron as an arrow in a box that represents the orbital •H, box labeled 1s with an upwards pointing arrow
8.27 What is effective nuclear charge? What is shielding?
•effective nuclear charge (Zeff): average/net charge from the nucleus experience by electrons in the outermost level •shielding: blocking of nuclear charge from outermost electrons •shielding primarily due to inner core electrons, although some interaction and shielding from electron repulsions of outer electrons with each other
8.30 How is the electron configuration of an anion different from that of the corresponding neutral atom? How is the electron configuration of a cation different?
•electron configuration of a main group monatomic ion deduced from electron configuration of neutral atom and charge of ion •anions- add number of electrons required by magnitude of the charge of the anions •cation, subtract number of electrons required by magnitude of the charge
8.16 What are valence electrons? Why are they important?
•important in chemical bonding •main group elements, in the outermost principal energy level •transition elements, also count outermost d electrons even though not in the outermost principal energy level •chemical properties of element depend on valence electrons •important in bonding because they are held most loosely •elemts in column of periodic table have similar chem properties because same number of valence electrons
8.20 Explain the relationship between a main-group element's lettered group number and it's valence electrons.
•lettered group number is equal to number of valence electrons for that element
8.28 Use concepts of effective nuclear charge, shielding and n value of the valence orbital to explain trend in atomic radius as you move across a period.
•n level stays the same •nuclear charge increases •amount of shielding stays the same because number of inner electrons stays the same •effective nuclear charge experienced by electrons in outermost principal energy level increases, resulting in a stronger attraction between outermost electrons and nuclear, and therefore a smaller atomic radii
8.18 Explain why S block only have two columns and p block has 6.
•number of columns correspond to max number of electrons that can occupy particular sub level of that block •s block has 2 columns corresponding to one s orbital holding 2 electrons •p block has six columns corresponding to three p orbitals with two electrons each
8.10 What is penetration? How does the penetration of an orbital into the region occupied by core elements affect the energy of an electron in that orbital?
•penetration: when an electron penetrates the electron cloud of the 1s orbital and experiences the charge of the nucleus more fully because it is less shielded •as outer electron undergoes penetration into the region occupied by inner electrons, experiences greater nuclear charge and, according to Coulomb's law, a lower energy
8.9 What is shielding? In an atom, which electrons tend to do the most shielding (core or valence)?
•shielding: one electron is blocked from full effects of the nuclear charge so that the electron experiences only part of the nuclear charge •Inner (core) electrons shield outer electrons from full nuclear charge
8.7 What is an electron configuration. Give an example.
•shows the particular orbitals that are occupied by electrons in an atom H= 1s1 He=1s2 Li= 1s2 2s1
8.11 Why are the sub levels within a principle level split into different energies for multi electron atoms but not for the hydrogen atom?
•sub levels for multi electron atoms split because penetration of the outer electrons into the region of the core electrons •sublevels not split because they are empty in the ground state
8.19 Why do rows in the periodic table get progressively longer as you move down the table? For example, first row has 2 elements, second has 8 elements, fourth and fifth have 18 elements.
•you are adding sub levels as n level increases
