SUMMARY OF ATOMIC MODELS
NAME / REPRESENTATION / MAIN IDEASDalton Model
“Billiard Ball” model / / 1. All matter is made up of tiny indivisible particles called atoms .
2. All atoms of the same element are the same in size , mass, etc.
3. Atoms of different elements are different in size and mass .
4. Atoms of different elements combine in small whole number ratios to form
molecules or compounds .
5. In chemical reactions, atoms are not created or destroyed . They are
rearranged or recombined .
Thomson Model
“ Raisin Bun ”
Model / / 1. the atom is a spherical cloud of positive charge with negatively charged
electrons embedded in it.
2. the amount of positive charge equals the amount of negative charge, so the entire atom is neutral.
Rutherford Model
“Solar system Model” / / 1. discovered using the gold foil . experiment.
2. the atom is mostly empty space.
3. most of the mass is concentrated in a small, dense nucleus .
4. electrons move around the nucleus like planets around the sun .
______Model
“Energy level” Model / / 1. electrons travel around the nucleus in specific energy levels .
2. if an atom is excited, electrons absorb a certain amount of energy and are boosted to a higher energy level.
3. electrons later drop back to a lower state releasing energy of a colour equal to the amount of energy released.
4. the first energy levels can hold a maximum of 2 electrons. The others have a valence shell of 8 electrons.
PROBABILITY
OBJECTIVE:
The purpose of this activity is to illustrate how probability and charge density are related to distance from the nucleus for the 1s orbital of a hydrogen atom. An analogy of throwing stones at a target will be used. The target is marked off in circles with radii increasing in 5 cm increments.
PROCEDURE:
1. Place the target on the desk. Stand back just beyond reach of the table edges and toss 100 stones at the target one at a time, always aiming for the centre.
2. Count the number of stones in each ring. Any stones which land on a line should be counted as landing in the inner ring.
RESULTS:
Ring Radius(cm) / Number of Hits (Your Data) / Number of Hits (Class Data)
0 - 5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
30 - 35
missed target
total throws
DATA ANALYSIS:
1. Plot the number of hits vs. the ring radius as a bar graph. Use the totals for the class.
Graph 1#
o
f
H
i
t
s
0 - 5 / 5 - 10 / 10 – 15
Radius / 15 - 20
(cm) / 20 - 25 / 25 - 30 / 30 - 35
2. What is the most probable distance from the center for the next stone to land?
At 5-10 cm radius.
3. Predict the probability of a hit in a ring 35 - 40 cm from the center. This can be done by extrapolation of the graph. The probability is the estimated number of hits divided by the total number of throws.
4. In the following chart:
a) calculate the area of each circle Use πr2
b) calculate the area of each ring by taking the difference in area between successive circles
c) calculate the density of hits for each ring; that is, the number of hits per square centimeter
Ring Radius(cm) / Area of Circle
(cm2) / Area of Ring
(cm2) / Density of Hits
(hits/cm2)
0 / 0
78.5
5 / 78.5
235.7
10 / 314.2
392.7
15 / 706.9
549.7
20 / 1256.6
706.9
25 / 1963.5
863.9
30 / 2827.4
1021.1
35 / 3848.5
5. Plot the density of hits vs. the ring radius as a bar graph.
Graph 2D o
e f
n
s H
i i
t t
y s
0 - 5 / 5 - 10 / 10 - 15 / 15 - 20
Radius (cm) / 20 - 25 / 25 - 30 / 30 - 35
6. How does the shape of this graph differ from the shape of the first graph?
The graph has the maximum value at the 1st ring not the 2nd.
7. Which graph most clearly shows that you were aiming at the centre of the target?
The 2nd graph shows that the center is where the stones were aimed at.
8. The shape of which graph combines the effect of aiming for the centre with the fact that the area decreases as the ring radius decreases?
The 2nd graph.
9. The following graph shows the probability of finding the electron at a distance r from the nucleus for the 1s orbital of hydrogen. Draw a vertical line showing the electron’s most probable distance from the nucleus.
10. There are two factors affecting the shape of this curve. These factors are analogous, but not identical to those affecting the shape of the bar graph in the stone throwing experiment.
(a) What factors in the atom would result in the electron tending to be close to the nucleus?
The electrostatic force and nuclear attraction.
(b) In spite of the previous factor, probability decreases as the distance from the nucleus decreases below that of the peak on the graph. Why is this so?
The volume of space is decreasing by radius cubed thereby decreasing the probability.
11. Imagine that the electron location possibilities represented as an analogy to the stone throwing activity. Sketch a graph of location density (#hits per unit volume) vs. distance r for the 1s orbital of a hydrogen atom using the graphs from the stone throwing activity as a guide.
Wave Functions and Quantum Numbers
1. -C-The number of orbitals in a given subshell, such as the 5d subshell, is determined by the number of possible values of
a) n b) l c) ml d) ms
2. -D-What are the possible values of n and ml for an electron in a 5d orbital?
a) n = 1, 2, 3, 4, or 5 and ml = 2 b) n = 1, 2, 3, 4, or 5 and ml = -2, -1, 0, +1, or +2
c) n = 5 and ml = 2 d) n = 5 and ml = -2, -1, 0, +1, or +2
3. -B-How many electrons can a single orbital hold?
a) 2n b) 2 c) 2l + 1 d) 8
4. -D-Which of the following is not a valid set of quantum numbers?
a) n = 2, l = 1, ml = 0, and ms = -1/2 b) n = 2, l = 1, ml = -1, and ms = -1/2
c) n = 3, l = 0, ml = 0, and ms = ½ d) n = 3, l = 2, ml = 3, and ms = ½
5. -B-What are the possible values of l if n = 5?
a) 5 b) 0, 1, 2, 3, or 4
c) -4, -3, -2, -1, 0, +1, +2, +3, or +4 d) -5, -4, -3, -2, -1, 0, +1, +2, +3, +4, or +5
6. -B-The subshell designations follow the alphabet after f. What is the first shell in which an h orbital would be allowed?
a) fifth b) sixth c) seventh d) eighth
7. -C-How many h orbitals are allowed in a given shell?
a) 5 b) 6 c) 11 d) 13
8. -C-What is the maximum number of orbitals in the seventh shell?
a) 4 b) 15 c) 49 d) 98
Orbital Shapes
9. -B-The orbital sketched below is found in the fifth shell. All lobes are depicted. Which orbital is consistent with this description?
a) 5p b) 5d c) 5f d) 4f
10. -C-The orbital sketched below is found in the third shell. All lobes are depicted. Which orbital is consistent with this description?
a) 3s b) 3d c) 3p d) 4f
Electron Configurations of Multielectron Atoms
11. -A-Which of the following represent electron configurations that violate the Aufbau principle?
(A) [Ne] 3s1 3p5 (B) [Kr] 5s2 4d10 5p3 (C) [Ar] 4s2 3d10 4p2
a) only (A) b) only (B) c) (A) and (B) d) (B) and (C)
12. -D-Which of the following represent electron configurations that are allowed but do not represent ground-state configurations?
(A) [Kr] 5s2 4d10 5p3 (B) [Ne] 3s1 3p5 (C) [Ar] 4s2 3d9 4p2
a) only (A) b) only (B) c) (A) and (B) d) (B) and (C)
13. -D-Which of the orbital-filling diagrams below would be disallowed by the Pauli exclusion principle?
4s 3d
(A) [Ar] ¯ ¯ ______
(B) [Ar] ______
(C) [Ar] ¯ ¯ ______
(D) [Ar] ¯ ______
(E) [Ar] ¯ ¯ ¯ ¯ ______
a) only (A) b) (A), (B), & (C) c) (A), (B), & (E) d) only (B)
14. -A-Which of the orbital-filling diagrams below would be disallowed by Hund’s Rule?
4s 3d
(A) [Ar] ¯ ¯ ______
(B) [Ar] ¯ ______
(C) [Ar] ¯ ¯ ______
(D) [Ar] ¯ ______
(E) [Ar] ¯ ¯ ¯ ¯ ______
a) only (A) b) (A), (B), & (C) c) (A), (B), & (E) d) only (B)
15. -C-What is the ground-state electron configuration of Co?
a) [Ar] 3d9 b) [Ar] 4s1 3d8 c) [Ar] 4s2 3d7 d) [Ar] 4s2 4p1 4d6
16. -C-How many unpaired electrons are in an atom of Co in its ground state?
a) 1 b) 2 c) 3 d) 7
17. -D-What is the ground-state electron configuration of tellurium?
a) [Kr] 5s2 3d10 5p4 b) [Kr] 5s2 5p6 c) [Kr] 5s2 5p4 d) [Kr] 5s2 4d10 5p4
18. -B-Which have the largest number of unpaired electrons in p orbitals in their ground-state electron configurations?
a) F, Cl, Br b) N, P, As c) Ne, Ar, Kr d) Te, I, Xe
19. -A-Which of the following have their valence electrons in the same energy level?
a) K, As, Br b) B, Si, As c) N, As, Bi d) He, Ne, F
20. -C-How many valence electrons does sulfur have?
a) 2 b) 4 c) 6 d) 16
PERIODIC PROPERTIES OF THE ATOM/ELECTRON
FACTORS TO CONSIDER
1. Coulomb’s Law:
where k is a constant, q is electrical charge, r is inter-particle distance and F is electrical force.
2. Nuclear charge, i.e. Z (Atomic Number).
3. Principal quantum number, i.e. principle energy level. The greater the principle energy level of the electron, the greater the time averaged distance from the nucleus (radius).
4. Shielding, i.e. the greater the number of inner principle energy level electrons (core electrons), the greater the outward repulsions on the valence electrons and the weaker the net force of attraction from the nucleus.
5. Sublevel or orbital type, eg. The orbital penetration of s orbital electrons inside the distance of maximum probability of p orbital electrons subjects them to a greater force of nuclear attraction and therefore a lower potential energy than the p orbital electrons even though they are in the same principle energy level, i.e. orbital splitting.
6. Charge distribution. Time averaged spherically symmetrical charge distributions experience fewer charge repulsions and are therefore more energetically favorable than non-spherically symmetrical distributions.
Explain the data in each of the following tables using all or some of the above factors.
GROUP 1 SUCCESSIVE IONIZATION ENERGIES
ELEMENT / LEVEL / IE(kJ/mol) / Z / n / shielding / orbital / symmetry / Therefore, \
Li
(relative to H) / 2 / 520 / / / / same / same / as you go down the column, each ion has the same electron configuration:
Z↑, \ FA↑
· n↑ and r↑ , \ FA¯¯
· Shielding is constant
· orbital is constant
· symmetry is constant
\ FA¯ overall and less energy is required to remove the valence electron
Na / 3 / 491 / / / / same / same
K / 4 / 414 / / / / same / same
Rb / 5 / 404 / / / / same / same
Cs / 6 / 376 / / / / same / same
INCREASING Z and IONIZATION ENERGY
Note: For e- - e- and symmetry, consider those effects once the e- is removed, the change.
Element and Z / IE(kJ/mol) / Electron configuration
Orbital box / n / shielding / r / orbital / e- - e-
change / symmetry change / Therefore, \
H / / 1310 /
He / / 2396 / ¯
/ same / same / ¯ / same / ¯¯ / same / Z, FA and IE
Li / / 520 /
/ / / / same / ¯ / same / n, r,
FA¯¯ and IE ¯¯
Be / / 901 / ¯
/ same / same / ¯ / same / ¯¯ / same / Z, FA and IE
B / / 805 / ¯ /
/ same / same / / / ¯ / / orbital , r, symm FA¯ and IE¯
C / / 1088 / ¯ / /
/ same / same / ¯ / same / ¯ / / Z, FA and IE
N / / 1396 / ¯ / / /
/ same / same / ¯ / same / ¯ / ¯¯ / symmetry¯, IE
O / / 1310 / ¯ / ¯ / /
/ same / same / ¯ / same / ¯¯ / / symmetry, IE ¯
F / / 1676 / ¯ / ¯ / ¯ /
/ same / same / ¯ / same / ¯¯ / / Z, FA and IE
Ne / / 2080 / ¯ / ¯ / ¯ / ¯
/ same / same / ¯ / same / ¯¯ / ¯¯ / Z, symmetry¯¯,
FA and IE
Na / / 491 /
/ / / / same / ¯ / same / n, r,
FA¯¯ and IE ¯¯
Mg / / 738 / ¯
/ same / same / ¯ / same / ¯¯ / same / Z, FA and IE
Al / / 641 / ¯ /
/ same / same / / / ¯ / / orbital , r, symm FA¯ and IE¯
Si / / 786 / ¯ / /
/ same / same / ¯ / same / ¯ / / Z, FA and IE
P / / 1060 / ¯ / / /
/ same / same / ¯ / same / ¯ / ¯¯ / symmetry¯, IE
S / / 1002 / ¯ / ¯ / /
/ same / same / ¯ / same / ¯¯ / / symmetry, IE ¯
Cl / / 1252 / ¯ / ¯ / ¯ /
/ same / same / ¯ / same / ¯¯ / / Z, FA and IE
Ar / / 1522 / ¯ / ¯ / ¯ / ¯
/ same / same / ¯ / same / ¯¯ / ¯¯ / Z, symmetry¯¯,
FA and IE
K / / 414 /
/ / / / same / ¯ / same / n, r,
FA¯¯ and IE ¯¯
Ca / / 587 / ¯
/ same / same / ¯ / same / ¯¯ / same / Z, FA and IE
CHEMICAL BONDING