Early Understanding of Matter
Name one of Dalton's postulates.
Dalton's Postulates:
1) The smallest indivisible building block of matter is the atom.
2) All atoms of a given element have identical mass and properties that distinguish them from atoms of other elements.
3) Atoms combine in simple, whole-number ratios to form molecules and compounds.
How many electrons can a p subshell hold?
6 electrons
The p subshell has 3 orbitals: px, py, and pz (3 different orientations of the dumbbell shape)
Each of the three orbitals can hold 2 electrons
What is the charge of ions formed by group 1A elements?
+1
How many atoms are in a 50g block of Mg?
1.24 x 1024 atoms
What class of molecules have the formula CnH2n+2 and how are they named?
Alkanes
They are named using a prefix (determined by the number of carbons they contain) + 'ane'
Ex: C5H12 -> pentane
Describe JJ Thomson's atomic model
In Thomson's model (Plum Pudding Model), small negatively charged particles (electrons) are dispersed within a positively charged electric field.
Which one of the following sets of quantum number is not possible?
A) n=4 l=3 ml=-2 ms=+1/2
B) n=3 l=0 ml=1 ms=-1/2
C) n=3 l=0 ml=0 ms=+1/2
D) n=2 l=1 ml=1 ms=-1/2
A) n=2 l=0 ml=0 ms=+1/2
B is not possible.
ml=1, but l=0
ml can only range from -l to +l
Put these elements in order of increasing atomic radius: Ga, Cs, S, F, Ca
F<S<Ga<Ca<Cs
What is the empirical formula of a compound that is 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen?
CH2O
Name this compound: P4S3.
Tetra phosphorous trisulfide
One of Dalton's postulates states that all atoms of a given element have identical mass and properties that distinguish them from atoms of other elements. Assess the accuracy of this statement.
We now know that isotopes exist, and atoms belonging to the same element do not have identical mass. However, atoms of the same element do share chemical properties and behaviors that distinguish them from atoms of other elements.
What is potassium's electron configuration?
1s2 2s2 2p6 3s2 3p6 4s1
How does the radius of Ca compare to Ca2+?
The radius of Ca is larger. Ca2+ has fewer electrons but the same number of protons. As a result, each electron in Ca2+ is pulled more strongly toward the nucleus, resulting in decreased radius.
Bromine (atomic mass 79.904 amu) has two naturally accruing isotopes,Br-79 and Br-81. The atomic mass of Br-81 is 80.1963 and its natural abundance is 49.04%. Calculate the mass and natural abundance of Br-79.
Abundance: 50.96%
Name the following two compounds: Au2O3 and Mg3P2.
Gold (III) oxide and magnesium phosphide
What were the key observations from Rutherford’s gold foil experiment, and how did these findings lead to the development of his atomic model?
Rutherford bombarded gold foil with a stream of small, positively charged particles. The majority of the particles passed through the foil undeflected, however, sometimes the particles were deflected at large angles or bounced back in the direction from which they had come.
Rutherford concluded that atoms contain mostly empty space and a dense, positively charged core. Electrons have little mass and are dispersed in the empty space in the atom surrounding the nucleus.
Calculate the energy (J) required to excite a hydrogen atom by causing an electronic transition from the n=1 to the n=4 principal energy level.
2.04 x 10-18 J
Which of these ionic solids would have the largest lattice energy?
A) SrO
B)NaF
C) CaBr2
D) CsI
E) BaSO4
A) SrO
Lattice energy increases as atomic radius of components decreases and charge of components increases
Terephthalic acid is an organic compound which is used to make clothing and plastic bottles. A sample of this compound contains 203.4g C, 12.7g H, and 135.6g O. Determine the empirical and molecular formula for this compound. (MW = 166.13 g/mol)
Empirical formula: C4H3O2
Molecular formula: C8H6O4
Write the chemical formula for hypochlorous acid.
HClO
What were the two major flaws in Rutherford’s atomic model, and what subsequent discovery helped resolve these issues?
Problem 1: His proposed nucleus would be unstable with only protons (positive-positive charge repulsion)
Problem 2: Atoms weighed more than Rutherford's model, consisting only of electrons and protons, predicted.
Discovery: neutrons
Give the electron configuration of lead in the noble gas format.
[Xe] 6s2 4f14 5d10 6p2
Put these elements in order of increasing ionization energy: Ga, Cs, S, F, Ca
Cs<Ga<Ca<S<F
Ga<Ca because of shielding from filled 3d subshell
Nonane is a colorless liquid that can be burned as fuel. If you have 7.29 x 1027 molecules of nonane, is it enough to fill a 20-gallon tank? (nonane density = 755 kg/m3, 1 gal = 0.00379 m3)
Yes (you have 542 gallons)
Write the chemical formula for lithium chlorate trihydrate.
LiClO₃ · 3H₂O