Chemistry Basics: Matter, Measurement, and Atomic Structure – Study Guide

Chemistry Basics: Matter and Measurement

Classification of Matter

Matter is anything that occupies space and has mass. It can be classified as a pure substance or a mixture. Pure substances include elements and compounds, while mixtures are categorized as homogeneous or heterogeneous.

• Pure Substances: Have a single chemical formula. Elements consist of only one type of atom (e.g., copper), while compounds are made of two or more atoms chemically combined (e.g., water).

• Mixtures: Contain two or more substances physically combined. Homogeneous mixtures are uniform throughout (e.g., brass), while heterogeneous mixtures have visibly different components (e.g., water and copper atoms).

States of Matter and Changes of State

Matter exists in three primary states: solid, liquid, and gas. Changes between these states occur through physical processes such as melting, freezing, vaporization, condensation, sublimation, and deposition.

• Solid ⇄ Liquid: Melting (solid to liquid) requires energy; freezing (liquid to solid) releases energy.

• Liquid ⇄ Gas: Vaporization (liquid to gas) requires energy; condensation (gas to liquid) releases energy.

• Solid ⇄ Gas: Sublimation (solid to gas) requires energy; deposition (gas to solid) releases energy.

• These are physical changes—the chemical identity remains unchanged.

Metric Units and Prefixes

The metric system uses base units for length (meter, m), volume (liter, L), and mass (gram, g; kilogram, kg). Prefixes modify these units to represent larger or smaller quantities.

• Common Prefixes: giga (G), mega (M), kilo (k), deci (d), centi (c), milli (m), micro (μ or mc), nano (n).

• Example: 1 kg = 1000 g; 1 g = 1000 mg.

Prefix	Abbreviation	Relationship to Base Unit
giga	G	× 1,000,000,000
mega	M	× 1,000,000
kilo	k	× 1,000
base unit	-	× 1
deci	d	÷ 10 = × 0.1
centi	c	÷ 100 = × 0.01
milli	m	÷ 1000 = × 0.001
micro	μ or mc	÷ 1,000,000 = × 0.000001
nano	n	÷ 1,000,000,000 = × 0.000000001

Unit Conversions and Dimensional Analysis

Unit conversions use conversion factors to change from one unit to another. Dimensional analysis is a systematic approach for solving these problems.

• Identify the unit for the final answer.

• Establish the given information.

• Determine conversion factors (e.g., 1 g = 1000 mg).

• Set up the equation so units cancel appropriately.

• Perform the calculation.

Scientific Notation and Percent Calculations

Scientific notation expresses numbers as a product of a coefficient and a power of ten. Percent calculations convert fractions to percentages.

• Scientific Notation: $number = a \times 10^n$ where $1 \leq a < 10$ and $n$ is an integer.

• Percent Calculation: $\text{Percent} = \frac{\text{part}}{\text{whole}} \times 100$

Number	Meaning	Scientific Notation
1,000,000	$10 \times 10 \times 10 \times 10 \times 10 \times 10$	$1 \times 10^6$
100,000	$10 \times 10 \times 10 \times 10 \times 10$	$1 \times 10^5$
10,000	$10 \times 10 \times 10 \times 10$	$1 \times 10^4$
1	1	$1 \times 10^0$
0.1	$1/10$	$1 \times 10^{-1}$
0.01	$1/(10 \times 10)$	$1 \times 10^{-2}$
0.000001	$1/(10 \times 10 \times 10 \times 10 \times 10 \times 10)$	$1 \times 10^{-6}$

Atoms and Radioactivity

Subatomic Particles

Atoms are composed of protons, neutrons, and electrons. Each has distinct properties and roles in atomic structure.

• Proton: Charge +1, mass 1 amu, located in the nucleus.

• Neutron: Charge 0, mass 1 amu, located in the nucleus.

• Electron: Charge -1, mass ~1/2000 amu, located outside the nucleus.

Subatomic Particle	Symbol	Electrical Charge	Relative Mass	Location in Atom
Electron	$e^-$	-1	0.0005 (1/2000)	Outside nucleus
Proton	$p$ or $p^+$	+1	1	Nucleus
Neutron	$n$ or $n^0$	0	1	Nucleus

Atomic Number, Mass Number, and Atomic Mass

The atomic number (Z) is the number of protons in the nucleus and defines the element. The mass number (A) is the sum of protons and neutrons in a specific atom. Atomic mass is the weighted average mass of all isotopes of an element.

• Atomic Number (Z): Identifies the element.

• Mass Number (A): Protons + Neutrons.

• Atomic Mass: Weighted average, not always a whole number.

Isotopes and Subatomic Particle Counts

Isotopes are atoms of the same element with different numbers of neutrons. The number of protons (atomic number) remains constant, while neutrons vary.

Subatomic Particle	Number in Atom
Protons	Atomic number (from periodic table)
Electrons	Equal to number of protons in a neutral atom
Neutrons	Mass number minus number of protons

Types of Nuclear Radiation

Nuclear radiation includes alpha, beta, gamma, positron, and neutron emissions, each with unique properties and symbols.

Emission	Symbol	Charge
Alpha	$\alpha$ or $^4_2He$	2+
Beta	$\beta$ or $^0_{-1}e$	1−
Gamma	$^0_0\gamma$	0
Positron	$^0_{1}e$	1+
Neutron	$^1_0n$	0

Penetrating Ability of Radiation

The ability of nuclear radiation to penetrate materials varies:

• Alpha: Least penetrating; stopped by paper or skin.

• Beta: Moderately penetrating; stopped by plastic or thin metal.

• Gamma: Most penetrating; requires thick lead or concrete.

Radioisotopes in Medicine

Radioisotopes are used in medicine for both diagnostic and therapeutic purposes. Diagnostic uses include imaging organs and tissues, while therapeutic uses involve targeting and destroying cancer cells.

Radioisotope	Clinical Use
Cesium-131	Brachytherapy in brain cancer
Fluorine-18	Cancer metabolism and tumor imaging
Iodine-123, Iodine-131	Thyroid imaging and uptake
Phosphorus-32	Bone marrow therapy, liver cancer therapy
Technetium-99m	Bone, kidney, breast tumor, heart, and lung perfusion imaging
Xenon-133	Lung function imaging

Additional Topics

Periodic Table and Element Classification

The periodic table organizes elements by atomic number and groups them by similar properties. Metals, nonmetals, and metalloids are distinguished by their location and characteristics.

Balancing Chemical Equations

Balancing chemical equations ensures the same number of atoms for each element on both sides of the equation. This is fundamental for representing chemical reactions accurately.

Element	Number in Reactants	Number in Products
H	4	4
C	1	1
O	4	4

Chemical vs. Physical Changes

Physical changes alter the form or appearance of a substance without changing its chemical identity. Chemical changes result in the formation of new substances.

• Physical Change: Melting, mixing, sawing.

• Chemical Change: Burning, rusting, spoiling.

Counting Atoms in Chemical Formulas

To determine the number of atoms of each element in a chemical formula, read the subscripts next to each element symbol. If no subscript is present, it means one atom.

• Example: In C6H12O6, there are 6 carbon, 12 hydrogen, and 6 oxygen atoms.

Summary Table: Subatomic Particles in Atoms

Subatomic Particle	Number in Atom
Protons	Atomic number
Electrons	Equal to protons (neutral atom)
Neutrons	Mass number minus atomic number

Summary Table: Types of Nuclear Radiation

Emission	Symbol	Charge
Alpha	$\alpha$ or $^4_2He$	2+
Beta	$\beta$ or $^0_{-1}e$	1−
Gamma	$^0_0\gamma$	0
Positron	$^0_{1}e$	1+
Neutron	$^1_0n$	0

Summary Table: Radioisotopes in Medicine

Radioisotope	Clinical Use
Cesium-131	Brachytherapy in brain cancer
Fluorine-18	Cancer metabolism and tumor imaging
Iodine-123, Iodine-131	Thyroid imaging and uptake
Phosphorus-32	Bone marrow therapy, liver cancer therapy
Technetium-99m	Bone, kidney, breast tumor, heart, and lung perfusion imaging
Xenon-133	Lung function imaging