What's the Matter?
What are the two defining characteristics of matter?
It has mass and occupies space (volume).
Which scientist discovered the electron using cathode-ray tube experiments?
J. J. Thomson
What is Avogadro's number, and what does it represent?
6.022 × 10²³ representative particles per mole
What are the horizontal rows and vertical columns of the periodic table called?
Rows = periods
Columns = groups or families
What is the difference between an intensive property and an extensive property? Give an example of each.
Intensive properties do not depend on the amount of matter (e.g., density)
Extensive properties do depend on the amount of matter (e.g., mass).
What is the difference between a homogeneous mixture and a heterogeneous mixture?
A homogeneous mixture has a uniform composition throughout, while a heterogeneous mixture has a nonuniform composition.
What did Rutherford's gold foil experiment reveal about the structure of the atom?
Atoms are mostly empty space with a small, dense, positively charged nucleus.
What is the relationship between the wavelength and frequency of electromagnetic radiation? If one increases, what happens to the other?
Wavelength and frequency are inversely proportional. As wavelength increases, frequency decreases, and vice versa.
What is the maximum number of electrons that can occupy each of the four sublevels: s, p, d, and f?
s = 2
p = 6
d = 10
f = 14
Which scientist proposed that electrons occupy specific, quantized energy levels around the nucleus?
Niels Bohr
Classify the following as a physical or chemical change:
(1) Melting ice
(2) Rusting iron
(3) Boiling water
(4) Burning wood
(1) Melting ice = physical
(2) Rusting iron = chemical
(3) Boiling water = physical
(4) Burning wood = chemical
An atom has 17 protons, 18 neutrons, and 17 electrons. Identify its element, atomic number, mass number, and overall charge.
Chlorine (Cl)
Atomic number = 17
Mass number = 35
Charge = 0 (neutral)
When an excited electron returns to a lower energy level, what happens to its energy, and what is emitted?
The electron releases energy in the form of a photon of light.
Write the full electron configuration for a neutral sulfur atom.
1s² 2s² 2p⁶ 3s² 3p⁴
What are the three fundamental subatomic particles, and which one determines the identity of an element?
Protons, neutrons, and electrons.
The number of protons determines the identity of an element (its atomic number).
A substance changes directly from a solid to a gas without becoming a liquid. What is this process called, and does it absorb or release energy?
Sublimation; it absorbs energy (endothermic).
Two atoms both contain 6 protons, but one has 6 neutrons and the other has 8 neutrons. What are these atoms called, and why are they still the same element?
Isotopes (carbon-12 and carbon-14). They are the same element because they have the same number of protons but different numbers of neutrons.
What is the mass of 2.00 moles of carbon dioxide (CO₂)? Use C = 12.01 g/mol and O = 16.00 g/mol.
Use the correct number of sig figs in your final answer.
Molar mass = 44.01 g/mol
2.00 mol CO2 × 44.01 g CO2/1 mol CO2
= 88.0 g CO₂
Write the noble-gas electron configuration for calcium.
[Ar] 4s²
An ion contains 12 protons, 12 neutrons, and 10 electrons. Identify the element, its mass number, and the charge of the ion.
Magnesium (Mg)
Mass number = 24
Charge = +2 (Mg²⁺)
A mixture contains sand, salt, and water. Explain how you could separate all three components and recover each one individually.
(1) Filtration to separate the sand
(2) Distillation (evaporation) to separate and collect the water
(3) Collect the salt left after distillation
Calculate the average atomic mass of an element that has two naturally occurring isotopes:
Isotope A has a mass of 10.0 amu and an abundance of 20.0%
Isotope B has a mass of 11.0 amu and an abundance of 80.0%.
(10.0 amu × 0.200) + (11.0 amu × 0.800)
Avg Atomic Mass = 10.8 amu
Calculate the frequency of light with a wavelength of 500 nm. Use c = 2.998 × 10⁸ m/s.
Use the exact calculated value for your final answer.
500 nm x (1 m/109 nm) = 5.00 x 10-7 m
ν = c/λ = (2.998 × 10⁸ m/s) / (5.00 × 10⁻⁷ m)
= 5.996 × 10¹⁴ Hz
A student draws the 2p orbital diagram for nitrogen as [↑↓] [↑] [ ].
Explain which electron-filling rule is violated and draw the correct 2p orbital diagram.
Hund's rule is violated because electrons must occupy equal-energy orbitals singly before pairing.
Correct 2p diagram: [↑] [↑] [↑]
An unknown element has the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁵.
Identify the element, its period, its group, and its number of valence electrons.
Chlorine (Cl)
Period 3
Group 17 (Halogens)
7 valence electrons