ch 9
What is an electron configuration? Give an example.
An electron configuration shows the particular orbitals that are occupied by electrons in an atom. Some examples are H=1s^1 He= 1s^2 and Li= 1s^2 2s^1
What is an orbital diagram? Provide an ex.
An orbital diagram is a different way to show the electron configuration of an atom. It symbolizes the electron as an arrow in a box that represents the orbital. The orbital for a hydrogen atom: (is a box with 1s under it and an H next to it. It has one arrow in it facing up)
Use concepts of effective nuclear charge, shielding, and n value of the valence orbital to explain the trend in atomic radius as you move across a period in the periodic table.
As you move to the right across a row in the periodic table, the n level stays the same. However, the nuclear charge increases and the amount of shielding stays about the same because the number of inner electrons stays the same. So the effective nuclear charge experienced by the electrons in the outermost principal energy level increases, resulting is a stronger attraction between the outermost electrons and the nuclease, and therefore, a smaller atomic radii.
the systematic pattern of filling up the electron configuration from low to high energy for an element is called
Aufbau principle
What is Coulomb's law? Explain how the potential energy of two charged particles depends on the distance between the charged and on the magnitude and sign of their charges.
Coulomb's law states that the potential energy (E) of two charged particles depends on their charges (q1 and q2) and on their seperation (r). R=1/4pi E (q1q2/r). The potential energy is positive for the charges of the same sign and negative for charges of the opposite sign. The magnitude of potential energy depends inversely on the seperation between the charged particles.
What are degenerate orbitals? According to Hund's rule, how are degenerate orbitals occupied?
Degenerate orbitals are orbitals of the same energy. In a multi-electron atom, the orbitals in a sub-levels are degenerate. Hund's rule states that when filling degenerate orbitals, electrons fill them singly first , with parallel spins. This is the result of an atom's tendency to find the lowest energy state possible.
Identify the isoelectronic elements
N3-, O2-, F-, Na+, Mg2+
Define atomic radius. For main-group elements, give the observed trends in atomic radius as you... a. Move across a period in the periodic table. b. Move down a column in the periodic table.
One way to define atomic radii is to consider the distance between nonbonding atoms in molecules or atoms that are touching each other bu are not bonded together. An atomic radius determined this way is called the nonbonding atomic radius or the van der Waals radius. The van der Waals radius represents the radius of an atom when it is not bonded to another atom. Another way to define the size of an atom , called bonding an atomic radius or covalent radius, is defined differently for nonmetals and metals as follows. Nonmetals: one-half the distance between two of the atoms bonded together Metal: one-half distance between two of the atoms next to each other in a crystal of the metal. A more general term, in the atomic radius, refers to a set of average bonding radii determined from measurements on a large number of elements and compounds. The atomic radius represents the radius of an atom when it is bonded to another atom and is always smaller than the van der Waals radius. a. As you move right across a period in a periodic table, atomic radius decreases b. As you move down a column in the periodic table, atomic radius increases
What is penetration? How does the penetration of an orbital into the region occupied by the core electrons affect the energy of an electron in that orbital?
Penetration occurs when an electron penetrates the electron cloud of the the 1s orbital and experiences the charge of the nucleus more fully because it is less shielded by the intervening electrons. As the outer electron undergoes penetration into the region occupied by the inner electrons, it experiences a greater nuclear charge and therefore, according to Coulumb's law, a lower energy.
What is shielding? In an atom, which electrons tend to do the most shielding (core electrons or valence electrons?)
Shielding or screening occurs when one electron is blocked from the full effects of the nuclear charge so that the electron experiences only a part of the nuclear charge. It is the inner (core) electrons that shield the outer electrons from the full nuclear charge
Why is electron spin important when writing electron configurations? Explain in terms of the Pauli exclusion principle.
The Pauli exclusion principle states the following: "No two electrons in an atom can have the same four quantum numbers." Because two electrons occupying the same orbital have three identical quantum numbers (n,l,m) they must have different spin quantum numbers. the Pauli exclusion principle impolies that each orbital can have a maximum of only two electrons, with opposing spins.
Explain the relationship between properties of an element and the number of valence electrons that it contains.
The chemical properties of elements are largely determined by the number of valence electrons they contain. Their properties are periodic because the number of valence electrons is periodic. Because elements within a column in the periodic table have the same number of valence electrons, they also have similar chemical properties.
What is effective nuclear charge? What is shielding?
The effective nuclear charge (Zeff) is the average or net charge from the nuclease experienced by the electrons in the outermost level. Shielding is the blocking of nuclear charge from the outermost electrons. The shielding is primarily due to the inner (core) electrons, although here is some interaction and shielding from the electron repulsions of outer electrons with each other.
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?
The electron configuration of a main-group monatomic ion can be deduced from the electron configuration of the neutral atom and the charge of the ion. For anions, we simply add the number of electrons required by the magnitude of the charge of the anion. The electron configuration of cations is obtained by subtracting the number of electrons required by the magnitude of the charge.
Explain the relationship between a main-group element's lettered group number and its valence electrons.
The lettered group number of a main-group element is equal to the number of valence electrons for that element.
Explain why the s block in the periodic table has only two columns why the p block has six.
The number of columns in a block corresponds to the maximum number of electrons that can occupy the particular sublevels of that block . The s block has two columns corresponding to one of the s orbitals holding a maximum of two electrons. The p block has six columns corresponding to the three p orbitals with two electrons each.
The periodic property is a result of periodic law. What observations led to periodic law? What theory explains the underlying reasons for the periodic law?
The periodic law was based on the observation that the properties of elements recur and certain elements have similar properties. The theory that explains the existence of the periodic law is quantum mechanical theory.
What are periodic properties?
The periodic property is predictable based on the elements position within the periodic table.
Why do the rows in periodic table get progressively longer as you move down the table? For ex., the first row contains 2 elements, the second and third rows each contain 8 elements, and the fourth and fifth rows each contain 18 elements. Explain,
The rows in the periodic table grow progressively longer because you are adding sublevels as the n level increases.
Why are the sublevels within a principal level split into different energies for multielectron atoms for the hydrogen atom?
The sublevels within a principle level split in multielectron atoms because of penetration of the outer electrons into the region of the core electrons. The sublevels in hydrogen are not split because they are empty in the ground state.
Explain how to write the electron configuration for an element based on its position in the periodic table.
To use the periodic table to write electron configuration, find the noble gas that precedes the element. The element has the inner electron configuration of that noble gas. Place the symbol for the noble gas in [ ]. Obtain the outer electron configuration by tracing the element across the period and assigning electrons in the appropriate orbitals.
What are valence electrons? Why are they important?
Valence electrons are important in chemical bonding. For main-group elements, the valence electrons are in the outermost principle energy level. For transition elements, we also count the outermost d electrons among the valence even though they are not in the outermost principal energy level. The chemical properties of an element depend on its valence electrons, which are important in bonding because they are held most loosely. This is why elements in a column of the periodic table have similar chemical properties, they have the same number of valence electrons.
List the number of valence electrons for each family in the periodic table, and explain the relationship between the number of valence electrons and the resulting chemistry of the elements in the family. a. Alkali b. Alkaline earth metals c. Halogens d. Oxygen family
a. The alkali metals (group 1A) have one valence electron and are among the most reactive metals because their outer electron configuration (ns^1) is one electron beyond a noble gas configuration. They react to lose the ns^1 electron, obtaining a noble gas configuration. This is why group 1A metals tend to form +1 cations b. The alkaline earth metals (group 2A) have two valence electrons, have an outer electron configuration of ns^2, and also tend to be reactive metals. They lose their ns^2 electrons to form 2+ cations. c. The halogens (group 7A) have seven valence electrons and have an outer electron configuration of ns^2np^5. They are among the most reactive nonmetals. They are only one electron short of noble gas configuration and tend to react to gain that one electron, forming 1- anions. d. The oxygen family (group 6A) has six valence electrons and has an outer electron configuration of ns^2np^4. They are two electrons short of noble configuration and tend to react to gain those two electrons, forming 2- anions.
How many valence electrons do the halogens possess? Select one: a. 5 b. 2 c. 7 d. 6 e. 1
c. 7
Identify the element that has a ground state electron configuration of [Kr]5s24d3 Select one: a. Mo b. Mn c. Nb d. Ru e. Tc
c. Nb
For a particular element, identify the species that has the largest radius. Select one: a. neutral b. They are all the same size c. anion d. radical e. cation
c. anion
The element that corresponds to the electron configuration 1s2 2s2 2p6 3s2 3p6 4s1 3d5 is Select one: a. manganese b. titanium c. chromium d. iron e. vanadium
c. chromium
Place the following in order of increasing metallic character. Rb Cs K Na Select one: a. K < Cs < Na < Rb b. Na < Rb < Cs < K c. Na < K < Rb < Cs d. Cs < Rb < K < Na e. K < Cs < Rb < Na
d. Cs < Rb < K < Na
When filling degenerate orbitals, electrons fill them singly first, with parallel spins. This way of filling orbitals is known as Select one: a. Coulomb's law b. the Aufbau principle c. the Heisenberg uncertainty principle d. the Pauli exclusion principle e. Hund's rule
e. Hund's rule
Choose the statement that is TRUE. Select one: a. All of the answers are correct b. Valence electrons are most difficult of all electrons to remove c. Outer electrons efficiently shield one another from nuclear charge d. Core electrons are the easiest of all electrons to remove e. Core electrons effectively shield outer electrons from nuclear charge
e. core electrons effectively shield outer electrons from nuclear charge
Give the set of four quantum numbers that represent the last electron added (using the Aufbau principle) to the Zn atom. Select one: a. n = 4, l = 3, ml = 3, ms = +1/2 b. n = 3, l = 2, ml = 2, ms = +1/2 c. n = 3, l = 1, ml = 1, ms = -1/2 d. n = 4, l = 6, ml = 0, ms = -1/2 e. n = 3, l = 2, ml = 2, ms = -1/2
e. n = 3, l = 2, ml = 2, ms = -1/2
What is electron affinity? What are the observed periodic trends in electron affinity?
left to right increases
What is metallic character? What are the observed periodic trends in metallic character?
right to left and top to bottom increases
