CHEM 1A Lecture Notes - Lecture 2: Electronic Correlation, Work Function, Band Diagram

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lemonwhale912

31 Oct 2017

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UC-Irvine

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Chemistry

Course

CHEM 1A

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Theresa Marie Mc Intire

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CHEM 1A Full Course Notes

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Below a certain energy threshold electrons will not be ejected regardless of the light intensity. Work function, band diagram for a metal. Case 1: no photoemission when hv is less than the work function. Case 2: hv=the work function of metal, no photoemission. Case 3: hv is greater than work function of metal, there is photoemission. Kinetic energy = every of photon - energy that binding. Less and equal to work function of metal is no photoemission. Greater than the work function of metal there is photoemission. Different metal have different thresholds because the possess different work functions but the slop is the same. P subshell (l=1) 3 orbitals (ml= -1,0,1) D subshell (l=2) 5 orbital (ml= -2,-1,0,1,2) Energy of electron is most dependent upon the shell number (4>3>2>1) Orbital sizes increases as n (quantum energy, size and energy) increases. Energy of electron in subshell increases moving from s to f.

Related Questions

1)The NaCl2 ionic salt does not exist. Which of the followingstatements best explains why?

A. Because the formation of Na2+ is an unfavorable process due tothe great amount of energy required to remove the 2nd electron fromthe Na atom (the 2nd electron would have to be removed from thecore electrons of the Na atom).
B. Because the Cl- anion is too large for there to be two of themattached to one Na+ ion.
C. Because NaCl2 is actually a polyatomic ion with a -1 charge, andnot an ionic salt. In the presence of another Na+ ion, the Na2Cl2salt would form.
D. Because Cl2 has no charge and therefore would not be attractedelectrostatically to the positively charged Na2+ cation.

2)Select the false statement below.

A. The first ionization energy of an atom is smaller than thesecond ionization energy of the same atom.
B. Phosphorus has a greater first ionization energy than magnesium,and the reason for this is because P has a greater effectivenuclear charge (Zeff) than Mg.
C. The following process is an endothermic process and representsthe first ionization energy of an atom A:A(g) ? A1+(g) + e1-
D. Fluorine has a greater first ionization energy than iodine, andthe reason for this is because fluorine has a greater amount ofshielding of outer electrons by inner electrons than doesiodine.

3)The Group 5A elements N,P,As have lower (less negative) electronaffinities than most of the Group 4A or Group 6A elements becauseN,P,As have half-filled subshells.

True
False

4)A fluorine atom is smaller than a bromine atom, and a potassiumatom is larger than a lithium atom.

True
False

5)A certain main-group element exhibits the following successiveionization energies in kJ/mol:

IE1 = 100; IE2 = 1200; IE3 = 2300; IE4 = 3100; IE5 = 4200

Select the false statement about this element below.

A. This is likely a Group 1A element.
B. This element is typically found uncombined in nature (that is,it is not usually found in compounds, but rather as a freeelement).
C. If this element is given a symbol of "J", it would form an ioniccompound with sulfur as J2S.
D. If this element was in period 2 of the periodic table, it wouldbe lithium.

6)Select the false statement below.

A. Generally speaking, non-metallic elements have greater effectivenuclear charge (Zeff) than metallic elements in the sameperiod.
B. Generally speaking, as you go down a group in the periodictable, there is successively greater shielding of the outer-shellelectrons by the inner-shell electrons.
C. Generally speaking, the heavier alkali metals can be predictedto exhibit greater shielding of the outer-shell electrons by theinner-shell electrons than lighter alkali metals.
D. Generally speaking, as you go across a period in the periodictable, the effective nuclear charge (Zeff) decreases because eachsuccessive element contains more protons in the nucleus than theprevious element and the outer electrons are all in the same shellas you go across a period.

7)Place the following in order of increasing size:

O2-, F1-, Li1+

A. F1- < Li1+ < O2-
B. Li1+ < O2- < F1-
C. Li1+ < F1- < O2-
D. F1- < O2- < Li1+

8)Select the false statement below.

A. The following set of quantum numbers is allowed:
n = 4, l = 2, ml = -2, ms = +1/2
B. The n = 1 shell of any given atom can accomodate up to 2electrons.
C. The n = 4 shell of any given atom can accomodate up to 16electrons.
D. In any given atom, the l = 2 subshell can accomodate up to 5electrons that have negative spins (ms =

redgoldfish403

The quantum rules any electron state are that n can be any integer > 1, l can be any positive integer less than n, m_l can be any integer from -l to +l, and m_s has only two possible values: Â±1/2.

a) Keeping the rule that n > 1, create an alternative universe by making a change to one of the other quantum rules â that is, change the restrictions on the allowed values of l, or m_l, or m_s. For example (no one can use these, of course), you might choose to say that l be any positive integer less than n² in the alternate universe. Or, you could say that m_s has seven possible values, -3, -2, -1, 0, 1, 2, or 3. The rule change can't restrict any of the quantum numbers to just one possible value. Don't copy alternative rules from any example â invent your own. You're welcome to send potential rules to the instructor for a check before proceeding.

b) Write out and count the total number of states in the two lowest energy shells (n = 1, n = 2) in your universe. Identify states by giving all four quantum numbers {n, l, m_l, m_s}, for example {2, 0, 0, +1/2}.

c) The so-called noble gases in our universe are (for the most part) atoms that, when neutral, have electrons completely filling every shell that has any electrons at all. For example, neutral helium (He) has 2 electrons, and there are two states in the n = 1 shell, so the electrons in He completely fill the first shell, and He is a noble gas. Given your results in (b), what would the first two noble gases be, in your universe? Explain.

CHEM 1A Lecture Notes - Lecture 2: Electronic Correlation, Work Function, Band Diagram

CHEM 1A Full Course Notes

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