REVIEW ACS I
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Question 1
How many atoms are in 2.17 g of Na? 
Explanation
2.17 g Na/ (22.9898 g/ mol Na) = 0.09439 mol Na * (6.022*10^23) = 5.68 * 10^22 atoms
Question 2
Which statement concerning the structure of the atom is correct? Select one: 
Question 3
What is the number of neutrons in the ion 80/35 Br-? Select one:
Explanation
80 (molar mass) Br – 35 (atomic #/ # of protons) 80 – 35 = 45 (# of neutrons)
Question 4
What is the expected empirical formula of gallium oxide? Select one:
Explanation
Gallium : Group 13 : Ga 3+ (2) Oxygen : Group 16 : O 2- (3) Its all about balance kiddos
Question 5
Which ion does not have 18 electrons? Select one:
Explanation
Sc 3+: 21e -3e = 18e Mn5+: 25e -5e = 20e K+: 19e-1e= 18e P3-: 15e+3e=18e one of these things is not like the other
Question 6
What is the maximum number of electrons that can occupy a px orbital? Select one:
Explanation
The MAX any orbital can hold is 2!!!!
Question 7
What is the valence electron configuration of the element in Period 4, Group 4A? Select one:
Explanation
lets be real this tripped me up for approximately ten minutes solely because i am apparently illiterate… the key word here is VALENCE as in only the outer shell so only level 4 energy levels should be included the element this question alludes to is Ge [ Period 4, Group 4a] and this element has a full 4s2 orbital and only 2 electrons in the p orbitals
Question 8
Four of the five d orbitals could be represented by Select one:
Explanation
s: spherical shape p: peanut shape d: double peanut shape
Question 9
For which of the following species does the Bohr model NOT work for determining the energy of an electron in an orbital? Select one:
Explanation
The Bohr model only works for elements and ions with 1 electron Extra Cool Stuff: This model depicts an atom as a solar system of sorts even though planets don’t circularly revolve around the sun, they go in a more elliptical fashion [ attraction is provided by electrostatic forces rather than gravity] Basically despite its extreme restrictions its still notable because of its success in explaining the Rydberg formula for the spectral emission lines of atomic hydrogen
Question 10
What is the electron configuration of Mn5+ in the ground state? Select one:
Explanation
According to the Aufbau principle electrons orbiting one or more atoms fill the lowest available energy levels before filling higher levels so 4s is filled before 3d, and one would assume when removed that 3d electron would be removed first but as per usual nothing is as it seems in chemistry apparently so the exact opposite occurs! And its not just because God is unjust and Butherus is coming after you personally but because as 3d fills up it’s energy levels decrease so 4s is removed first as it has the highest energy
Question 11
Which electron configuration is impossible? (Careful, excited states are possible.) Select one:
Explanation
2d does not exist as a state or configuration
Question 12
How many unpaired electrons does Co2+ have? Select one:
Explanation
2 electrons are removed from the 4s level leaving the 3d level the same with 7 electrons and 3 unpaired electrons
Question 13
which of these species is paramagnetic? Select one:
Explanation
Remember the Mn5+ structure you probably drew or thought up earlier. it only has one unpaired electron, therefore it is paramagnetic
Question 14
Which of these diagrams could represent the ground state of the d valence electrons of V? Select one:
Explanation
Due to the Hund’s Rule and Pauli Exclusion principle it can’t be A or C. Basically electrons need to be spinning the same way, until they get partners that will spin the other way. And that electrons can’t be paired until every sub orbital is filled. And because V only has three electrons in the d level we are left with B.
Question 15
Which emission line in the hydrogen spectrum occurs at the longest wavelength? Select one:
Explanation
Use the Rydberg formula: 
is the wavelength of the light emitted in vacuum; 
is the Rydberg constant for this element; for H it’s 1.097373*10^7 m^-1 
is the atomic number 
and 
, n are integers such that n
, corresponding to the principal quantum numbers of the orbitals occupied before and after. The smaller the energy emitted the longer the wavelength
Question 16
The element X occurs naturally to the extent of 72.25% 30X and the rest 32X. What is the atomic mass of X? (Use 4 sig. fig.)
Explanation
0.7225(30) + (1-0.7225)(32) = 30.55
Question 17
Which set of quantum numbers is correct and consistent with n = 3? (l = angular momentum quantum number, ml = magnetic q.n., and ms = electron spin q.n.) Select one:
Explanation
n=3 –> principle quantum number (n) –> describes the size of the orbital [indirectly describes the energy of an orbital] l= 0,1,2 –> can be any integer between 0 and (n-1) ml: 0, -1<m<1, -2<m<2 –> any integer between -1 and l ms: +1/2 or -1/2 It can’t be A (ml) or C (l) or D (ms).
Question 18
Which element is represented by 33/11X?Select one:
Explanation
33 X 11 11 protons/ atomic # = Na (sodium)