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What are the three main subatomic particles and their charges?

• Proton: Positive (+1)
• Neutron: Neutral (0)
• Electron: Negative (–1)

How do you determine the number of protons, neutrons, and electrons in an atom?

• Protons = Atomic number
• Electrons = Atomic number (in a neutral atom)
• Neutrons = Mass number – Atomic number

What is an isotope?

Atoms of the same element with different numbers of neutrons (and therefore different mass numbers).

What is the difference between atomic number and mass number?

• Atomic number = Number of protons
• Mass number = Protons + Neutrons

What trend in the periodic table explains the increase in atomic radius?

Atomic radius increases down a group due to added electron shells and decreases across a period due to increased nuclear charge pulling electrons closer.

Define electronegativity and explain its trend.

Electronegativity is the ability of an atom to attract electrons in a bond.
• Increases across a period
• Decreases down a group

Why are noble gases unreactive?

They have full outer electron shells (complete octet), making them stable and unlikely to form bonds.

Which group contains the alkali metals? Halogens?

• Alkali metals: Group 1
• Halogens: Group 17

What is the difference between ionic, covalent, and metallic bonding?

• Ionic: Transfer of electrons between a metal and nonmetal
• Covalent: Sharing of electrons between two nonmetals
• Metallic: Free-floating electrons shared among metal atoms

What type of elements form ionic bonds?

Metals and nonmetals

How do you determine the polarity of a molecule?

Check:

1. Bond polarity (difference in electronegativity)
2. Molecular shape (symmetrical = nonpolar, asymmetrical = polar)

What is the octet rule?

Atoms tend to gain, lose, or share electrons to achieve 8 electrons in their outer shell.

Balance this chemical equation:
__Al + __O₂ → __Al₂O₃

4Al + 3O₂ → 2Al₂O₃

Identify the type of reaction:
• Synthesis
• Decomposition
• Single replacement
• Double replacement
• Combustion

Examples:
• Synthesis: A + B → AB
• Decomposition: AB → A + B
• Single replacement: A + BC → AC + B
• Double replacement: AB + CD → AD + CB
• Combustion: Hydrocarbon + O₂ → CO₂ + H₂O

What is the law of conservation of mass?

Mass is neither created nor destroyed in a chemical reaction — total mass of reactants = total mass of products.

What is a mole? How many particles are in a mole?

A mole is 6.022 \times 10^{23} particles (Avogadro’s number).

How do you convert grams to moles? Moles to molecules?

• Grams → Moles: divide by molar mass
• Moles → Molecules: multiply by 6.022 \times 10^{23}

If 2.00 moles of H₂ react with O₂, how many grams of H₂O are produced?

Reaction: 2H₂ + O₂ → 2H₂O
• 2 mol H₂ → 2 mol H₂O
• Molar mass of H₂O = 18.02 g/mol
→ 2 mol H₂O × 18.02 g/mol = 36.04 g H₂O

What are the properties of solids, liquids, and gases?

• Solids: Fixed shape and volume, particles tightly packed
• Liquids: Definite volume, no fixed shape, particles close but can move
• Gases: No fixed shape or volume, particles spread out and fast-moving

State and explain Boyle’s Law and Charles’s Law.

• Boyle’s Law: P1V1 = P2V2 (Pressure and volume inversely related at constant temperature)
• Charles’s Law: \frac{V1}{T1} = \frac{V2}{T2} (Volume and temperature directly related at constant pressure)

What is the ideal gas law?

PV = nRT
• P = pressure
• V = volume
• n = moles
• R = gas constant (0.0821 L·atm/mol·K)
• T = temperature in Kelvin

A gas occupies 5.00 L at 1.00 atm. What will the volume be at 2.00 atm if temperature stays constant?

Use Boyle’s Law: P1V1 = P2V2
(1.00)(5.00) = (2.00)V2 → V2 = 2.50 \, \text{L}