CHEM 1150 Exam 1 Study Guide: GOB Chemistry Fundamentals

Chemistry Basics – Matter and Measurements

Classification of Matter

Understanding the basic classification of matter is essential in chemistry. Matter can be categorized as elements, compounds, or mixtures, which may be homogeneous or heterogeneous.

• Element: A pure substance consisting of only one type of atom (e.g., O2, Fe).

• Compound: A substance formed from two or more elements chemically bonded (e.g., H2O, NaCl).

• Mixture: A combination of two or more substances not chemically bonded. Homogeneous mixture: Uniform composition (e.g., saltwater). Heterogeneous mixture: Non-uniform composition (e.g., salad).

Periodic Table Fundamentals

The periodic table organizes elements by atomic number and properties. Key features include periods (rows), groups (columns), and the staircase dividing metals and nonmetals.

• Periods: Horizontal rows indicating energy levels.

• Groups: Vertical columns with similar chemical properties.

• Staircase: Separates metals (left) from nonmetals (right).

• Common elements: H, He, Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Fe, Cu, Zn, Ag, Au, Pb, Sn.

Chemical Symbols and Names

Chemical symbols are one- or two-letter abbreviations for elements (e.g., Na for sodium, Cl for chlorine).

• Example: Fe = iron, Pb = lead, Ag = silver.

Physical and Chemical Properties

Properties help distinguish substances and predict behavior.

• Physical properties: Observable without changing composition (e.g., melting point, density).

• Chemical properties: Describe reactivity and ability to form new substances (e.g., flammability).

Significant Figures and Calculations

Significant figures reflect the precision of measurements. Calculations must maintain correct significant figures.

• Rules: All nonzero digits are significant; zeros between significant digits are significant; leading zeros are not significant; trailing zeros are significant only if there is a decimal point.

• Example: 0.00520 has three significant figures.

Unit Conversions and SI Units

SI units are the standard units in science. Common conversions include length, mass, and temperature.

• Length: 1 in = 2.54 cm (exact), 1 m = 100 cm

• Mass: 1 lb = 0.4536 kg

• Temperature: $^ ext{o}C = rac{5}{9} (^ ext{o}F - 32)$

Density and Specific Gravity

Density is mass per unit volume; specific gravity compares density to water.

• Density formula: $ext{Density} = rac{ ext{Mass}}{ ext{Volume}}$

• Specific gravity: $ext{Specific gravity} = rac{ ext{Density of substance}}{ ext{Density of water}}$

Heat Capacity and Energy

Heat capacity is the amount of heat required to change a substance's temperature.

• Heat capacity formula: $q = m imes c imes riangle T$ where q = heat, m = mass, c = specific heat, ΔT = temperature change.

Atoms and Radioactivity

Atomic Structure

Atoms consist of protons, neutrons, and electrons. Atomic number and mass number define the element and isotope.

• Proton: Positively charged particle in nucleus.

• Neutron: Neutral particle in nucleus.

• Electron: Negatively charged particle in orbitals.

• Atomic number (Z): Number of protons.

• Mass number (A): Number of protons + neutrons.

• Isotope: Atoms of the same element with different numbers of neutrons.

Radioactivity and Types of Radiation

Radioactive decay involves emission of particles or energy from unstable nuclei.

• Alpha (α) radiation: Emission of helium nuclei ($^4_2 ext{He}$).

• Beta (β) radiation: Emission of electrons ($^0_{-1} ext{e}$).

• Gamma (γ) radiation: Emission of high-energy photons.

Effects and Applications of Radiation

• Biological effects: Radiation can damage cells and DNA.

• Medical applications: Used in cancer treatment, imaging, and sterilization.

Balancing Nuclear Equations

Nuclear equations must balance mass and atomic numbers.

• Example: $^{14}_6 ext{C} ightarrow ^{14}_7 ext{N} + ^0_{-1} ext{e}$

Units of Radiation

• Becquerel (Bq): SI unit for radioactivity.

• Gray (Gy): SI unit for absorbed dose.

• Sievert (Sv): SI unit for biological effect.

Electrons and Bonding

Valence Electrons and the Octet Rule

Valence electrons are electrons in the outermost shell. The octet rule states that atoms tend to gain, lose, or share electrons to achieve eight in their valence shell.

• Valence electrons: Determine chemical reactivity.

• Octet rule: Atoms achieve stability with eight valence electrons.

Ions and Polyatomic Ions

Ions are charged particles formed by gaining or losing electrons. Polyatomic ions are groups of atoms with a charge.

• Cation: Positively charged ion (loss of electrons).

• Anion: Negatively charged ion (gain of electrons).

• Polyatomic ions: Examples include NO3-, SO42-, CO32-, PO43-, CH3CO2-, OH-, CN-, NH4+.

Electron Configuration and Periodic Trends

Electron configuration describes the arrangement of electrons in energy levels. Periodic trends include atomic size, ionization energy, and electronegativity.

• Example: Sodium (Na): 1s2 2s2 2p6 3s1

• Periodic trends: Atomic size increases down a group, decreases across a period; ionization energy and electronegativity increase across a period.

Electron Gain/Loss for Octet

Main group elements gain or lose electrons to achieve a full octet or stable charge.

• Example: Na loses one electron to form Na+; Cl gains one electron to form Cl-.

Summary Table: Key Terms and Definitions

Term	Definition	Example
Element	Pure substance of one type of atom	O2, Fe
Compound	Substance of two or more elements chemically bonded	H2O, NaCl
Mixture	Physical blend of two or more substances	Air, salad
Isotope	Atoms of same element with different neutrons	C-12, C-14
Cation	Positively charged ion	Na+
Anion	Negatively charged ion	Cl-
Polyatomic Ion	Charged group of covalently bonded atoms	SO42-
Alpha Radiation	Helium nucleus emission	$^4_2 ext{He}$
Beta Radiation	Electron emission	$^0_{-1} ext{e}$
Gamma Radiation	High-energy photon emission	γ-ray

Additional info: Academic context and examples have been expanded for clarity and completeness.