General Chemistry Overview

What are atoms composed of?

Atoms consist of a nucleus made of protons and neutrons, surrounded by electrons arranged in shells.

What defines the element of an atom?

The number of protons in the atom defines the element.

What are valence electrons and why are they important?

Valence electrons are the outermost shell electrons that play a critical role in chemical behavior.

How are elements organized in the periodic table?

Elements are organized systematically, with those in the same group sharing the same number of valence electrons and those in the same period sharing the same number of electron shells.

What is the significance of isotopes?

Isotopes are variants of elements that differ in neutron number, often being unstable and radioactive.

What distinguishes cations from anions?

Cations are positively charged ions, while anions are negatively charged ions.

What are the three categories of elements in the periodic table?

Elements are categorized into metals (left), nonmetals (right), and semimetals (along the dividing line).

What is the difference between molecules and compounds?

Molecules are formed from two or more atoms bonded together, while compounds contain at least two different elements.

What are isomers?

Isomers are compounds that share the same molecular formula but differ structurally.

What do Lewis dot structures represent?

Lewis dot structures visually represent valence electrons and bonds between atoms.

What type of bond forms when electrons are shared?

Covalent bonds form when atoms share electrons.

How does electronegativity influence bonding?

Electronegativity, the atom's pull on electrons, influences the type of bond formed; higher differences can lead to ionic bonds.

What characterizes ionic bonds?

Ionic bonds form when one atom donates an electron (cation) and another accepts it (anion), typically when the electronegativity difference exceeds about 1.7.

What is a metallic bond?

Metallic bonds are characterized by a lattice of positive ions surrounded by delocalized, mobile electrons.

What defines polar covalent bonds?

Polar covalent bonds occur when electrons are unequally shared between atoms, creating dipoles.

What is a classic example of a polar molecule?

Water is a classic polar molecule, with oxygen being partially negative and hydrogens being partially positive.

What are intermolecular forces (IMFs)?

Intermolecular forces are interactions between polar molecules, including hydrogen bonds and Van der Waals forces.

How does water's polarity affect its solubility?

Water's polarity makes it an excellent solvent for polar or charged substances but unable to dissolve nonpolar molecules like oils.

What role do hydrogen bonds play in physical properties?

Hydrogen bonds influence physical properties such as boiling points and solubility.

What happens to atomic mass in the periodic table as you move left to right?

Atomic mass generally increases from left to right due to added protons, neutrons, and electrons.

What is the relationship between group number and valence electrons in main groups?

For main groups, the group number (1 to 8) corresponds to the number of valence electrons, except for helium.

What does the saying 'like dissolves like' mean in chemistry?

Polar solvents dissolve polar solutes, while nonpolar solvents dissolve nonpolar solutes.

How do soaps function in cleaning?

Soaps have polar heads and nonpolar tails that surround nonpolar dirt in water, forming micelles that wash away grime.

What are the three main states of matter?

Solids, liquids, and gases.

How do solids, liquids, and gases differ in terms of particle arrangement and behavior?

Solids have fixed particle arrangements; liquids flow but retain volume; gases expand to fill their containers.

What is temperature a measure of in terms of particle behavior?

Temperature measures average particle kinetic energy.

What does entropy quantify in a system?

Entropy quantifies disorder within a system.

What conditions favor the formation of solids and gases?

Low temperature/high pressure favors solids (low entropy), while high temperature/low pressure favors gases (high entropy).

Why do salts remain solid at room temperature while water is liquid?

Strong ionic bonds in salts raise their melting points.

What is plasma and where is it commonly found?

Plasma is an ionized gas found in stars and neon lights, where high energy excites electrons.

How are pure substances and mixtures defined in chemistry?

Pure substances consist of a single element or compound, while mixtures are combinations of substances.

What is the difference between homogeneous and heterogeneous mixtures?

Homogeneous mixtures have uniform composition (e.g., saltwater), while heterogeneous mixtures have distinct regions (e.g., sand in water).

What are colloids and how do they differ from solutions?

Colloids, like milk, have particles dispersed but not fully dissolved, allowing a uniform appearance but larger particle size than solutions.

What are the main types of chemical reactions?

Synthesis, decomposition, single replacement, and double replacement.

What principle must chemical reactions obey regarding mass?

Chemical reactions must obey the conservation of mass, balancing atom counts on both sides.

What is stoichiometry and why is it important?

Stoichiometry uses mole ratios based on atomic masses to measure reactants accurately, enabling precise laboratory measurements.

What distinguishes physical changes from chemical changes?

Physical changes alter appearance without changing the substance, while chemical changes alter substances and often produce visual or sensory clues.

What is activation energy in the context of chemical reactions?

Activation energy is the energy needed to start a reaction.

How do catalysts affect activation energy?

Catalysts lower the activation energy barrier without being consumed, speeding up reactions.

What does enthalpy represent in a chemical reaction?

Enthalpy represents internal heat energy.

What defines an exothermic reaction?

An exothermic reaction decreases enthalpy, releasing heat.

What defines an endothermic reaction?

An endothermic reaction increases enthalpy, absorbing heat.

What is Gibbs free energy and its significance in reactions?

Gibbs free energy change (ΔG) indicates spontaneity; reactions are spontaneous if ΔG is negative.

What is the Brønsted-Lowry definition of acids and bases?

Acids are proton (H⁺) donors, and bases are proton acceptors.

What is the relationship between pH and hydronium ion concentration?

pH is the negative logarithm of hydronium ion concentration, with each unit change corresponding to a tenfold concentration change.

What occurs during acid-base neutralization?

Acid-base neutralization forms water and salt.

What are redox reactions and what do they involve?

Redox reactions involve electron transfer, changing the oxidation states of elements.

What is the significance of oxidation numbers in redox reactions?

Oxidation numbers help track electron flow and identify oxidants and reductants.

How are redox reactions balanced in acid or base?

Balancing redox reactions requires adding ions and water to maintain charge and atom balance.

What are the four quantum numbers that describe electron orbitals?

n (shell), l (subshell shape: s, p, d, f), ml (orbital orientation), ms (spin: ±½)

What is the Pauli exclusion principle?

Each orbital can hold two electrons with opposite spins.

How many electrons can each subshell hold?

s holds 2, p holds 6, d holds 10, and f holds 14.

What does the Aufbau principle state about electron configuration?

Electrons fill lower energy subshells first.

What is the significance of electron configurations in chemistry?

They specify how electrons are distributed, helping identify valence electrons, especially for transition metals.

What defines the element in an atom?

The number of protons in the nucleus.

What are valence electrons?

Electrons in the outermost shell that are crucial for chemical reactions.

What do elements in the same group of the periodic table have in common?

They have the same number of valence electrons, resulting in similar chemical properties.

What is the octet rule?

Atoms bond to achieve a more stable state by filling their outer electron shells with eight electrons, except for hydrogen and helium which require two.

What are isotopes?

Atoms of the same element with different numbers of neutrons.

What are ions?

Charged atoms formed by the loss or gain of electrons; negative ions are anions, positive ions are cations.

How does electronegativity vary in the periodic table?

Electronegativity increases from bottom left to top right.

What is the role of covalent bonds in chemical bonding?

Covalent bonds are formed by sharing electrons between atoms to fill outer shells.

What is the relationship between atomic structure and chemical behavior?

The configuration of electrons, especially valence electrons, determines an element's chemical behavior.

What are the main components of an atom?

A nucleus formed by protons and neutrons, surrounded by electrons.

What is the importance of understanding atomic structure in chemistry?

It provides a comprehensive foundation for understanding chemistry's core principles.

What is the significance of the periodic table's organization?

It reflects the increasing mass of elements from left to right due to the addition of protons, neutrons, and electrons.

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What defines nonpolar covalent bonds and their electronegativity difference?

Electrons are shared equally with an electronegativity difference of less than 0.5.

What characterizes polar covalent bonds?

Unequal sharing of electrons creates partial charges, with an electronegativity difference between 0.5 and 1.7.

Provide an example of a polar covalent bond.

Water (H₂O), where oxygen is partially negative and hydrogen is partially positive.

What occurs in ionic bonds and what is their electronegativity difference?

A large electronegativity difference greater than 1.7 causes full electron transfer, forming ions.

Give an example of an ionic bond.

Sodium chloride (table salt), where sodium loses an electron and chlorine gains one.

What are metallic bonds and how do they contribute to metallic properties?

Valence electrons are delocalized and free to move across a lattice of positive metal nuclei, explaining properties like conductivity and malleability.

What is a molecular formula?

A formula that counts atoms but cannot distinguish isomers.

What do Lewis-dot structures represent?

They show valence electrons and bonding in a molecule.

What defines hydrogen bonds?

Strong dipole interactions involving hydrogen and highly electronegative atoms such as fluorine, oxygen, or nitrogen.

What are Van der Waals forces?

Temporary dipoles that occur due to electron movement, even in nonpolar molecules.

What are the three primary states of matter?

Solids, liquids, and gases.

Describe the particle arrangement in solids.

Particles are tightly packed with fixed positions and can only vibrate.

How do particles behave in liquids?

Particles move freely but remain close together, maintaining volume.

What characterizes gas particles?

Particles move independently and fill the container they are in.

What is plasma?

An ionized gas at very high temperatures or electric potentials, such as in stars or neon lights.

What does temperature measure in the context of matter?

The average kinetic energy of particles.

What is entropy?

The degree of disorder or randomness in a system.

How do strong bonds affect melting points?

Strong bonds, like ionic bonds, result in high melting points due to the energy required to break them.

What are the two types of mixtures?

Homogeneous (uniform composition) and heterogeneous (non-uniform composition).

What is a colloid?

An intermediate mixture where particles are dispersed but not fully dissolved, such as milk.

What role do surfactants play in mixtures?

Surfactants have both polar heads and nonpolar tails that can form micelles to trap nonpolar substances in water.

What are the four main types of chemical reactions?

Synthesis, decomposition, single replacement, and double replacement.

What is stoichiometry?

The calculation of reactant and product quantities based on balanced chemical equations, respecting the conservation of mass.

What is a mole in chemistry?

A unit representing Avogadro's number (6.022 × 10²³ particles), used to measure amounts in reactions.

What is activation energy?

The energy needed to initiate a reaction, which can be lowered by catalysts.

What distinguishes exothermic and endothermic reactions?

Exothermic reactions release heat (ΔH < 0), while endothermic reactions absorb heat (ΔH > 0).

What does Gibbs Free Energy (ΔG) indicate about a reaction?

ΔG combines enthalpy and entropy changes to determine spontaneity; ΔG < 0 indicates a spontaneous reaction, while ΔG > 0 indicates a non-spontaneous reaction.

How does temperature influence the spontaneity of melting ice?

Melting ice is endothermic but spontaneous above 0°C due to increased entropy.

What defines chemical equilibrium?

Chemical equilibrium occurs in reversible reactions where the forward and reverse rates balance, keeping concentrations stable.

What do Brønsted-Lowry acids and bases do?

Acids donate protons (H⁺) and bases accept protons; after the reaction, they become conjugate bases and conjugate acids respectively.

What are amphoteric substances?

Amphoteric substances can act as both acids and bases.

What does the pH scale measure?

The pH scale measures acidity based on hydronium ion concentration, where pH = -log[H₃O⁺].