10th Class Chemistry: Atomic Structure & Reactions

Atomic Structure

• Atoms: Basic units of matter; composed of protons, neutrons, and electrons.
• Nucleus: Center of the atom containing protons and neutrons.
• Electrons: Negatively charged particles orbiting the nucleus in energy levels.
• Protons: Positively charged particles; determine the atomic number.
• Neutrons: Neutral particles; contribute to the atomic mass.
• Isotopes: Atoms of the same element with different numbers of neutrons.

Chemical Reactions

• Definition: Process where substances (reactants) transform into different substances (products).
• Types of Reactions:
  • Synthesis: A + B → AB
  • Decomposition: AB → A + B
  • Single Replacement: A + BC → AC + B
  • Double Replacement: AB + CD → AD + CB
• Conservation of Mass: Mass is conserved in a chemical reaction; the mass of reactants equals the mass of products.
• Exothermic Reactions: Release energy (heat).
• Endothermic Reactions: Absorb energy (heat).

Periodic Table

• Organization: Elements arranged by increasing atomic number and grouped by similar properties.
• Groups: Columns on the periodic table; elements in a group have similar chemical properties.
• Periods: Rows on the periodic table; indicate the number of electron shells.
• Metals, Nonmetals, Metalloids:
  • Metals: Good conductors, malleable, ductile.
  • Nonmetals: Poor conductors, brittle, varied states at room temperature.
  • Metalloids: Properties of both metals and nonmetals.
• Key Groups:
  • Alkali Metals (Group 1): Highly reactive, especially with water.
  • Alkaline Earth Metals (Group 2): Reactive, but less so than alkali metals.
  • Noble Gases (Group 18): Inert, non-reactive gases.

Acids and Bases

• Acids: Substances that donate protons (H+) in solution; have a sour taste.
• Bases: Substances that accept protons or donate hydroxide ions (OH-) in solution; have a bitter taste and slippery feel.
• pH Scale: Measures the acidity or basicity of a solution (0-14 scale).
  • Acidic: pH < 7
  • Neutral: pH = 7
  • Basic: pH > 7
• Neutralization: Reaction between an acid and a base to produce salt and water.

Atomic Number and Mass Number

• Atomic Number (Z): Number of protons in the nucleus; defines the element.
• Mass Number (A): Total number of protons and neutrons in the nucleus.
  • Calculation: Mass Number = Number of Protons + Number of Neutrons.
• Example: Carbon has an atomic number of 6 (6 protons) and a mass number of 12 (6 protons + 6 neutrons).

Atomic Structure

• Atoms are the fundamental building blocks of matter.
• The nucleus is the atom's core, containing protons (positively charged) and neutrons (neutral).
• Electrons are negatively charged particles that orbit the nucleus in distinct energy levels.
• The number of protons in an atom dictates its atomic number and defines the element.
• Isotopes are variations of the same element that differ in neutron count.

Chemical Reactions

• Chemical reactions involve the transformation of reactants into products.
• Types of reactions include:
  • Synthesis (A + B → AB) combines two substances.
  • Decomposition (AB → A + B) breaks down a compound.
  • Single Replacement (A + BC → AC + B) exchanges components between compounds.
  • Double Replacement (AB + CD → AD + CB) involves mutual exchange of components.
• Mass remains constant throughout a reaction; the mass of reactants equals the mass of products.
• Exothermic reactions release heat energy, while endothermic reactions absorb it.

Periodic Table

• The periodic table organizes elements by increasing atomic number and groups them by similar properties.
• Groups (columns) consist of elements with shared chemical characteristics, while periods (rows) indicate the number of electron shells.
• Metals are conductive, malleable, and ductile; nonmetals are poor conductors and brittle; metalloids exhibit properties of both.
• Key element groups include:
  • Alkali Metals (Group 1): Highly reactive, particularly with water.
  • Alkaline Earth Metals (Group 2): Reactive but less so than alkali metals.
  • Noble Gases (Group 18): Inert and non-reactive.

Acids and Bases

• Acids are substances that release protons (H+) and typically have a sour taste.
• Bases accept protons or release hydroxide ions (OH-), resulting in a bitter taste and slippery texture.
• The pH scale ranges from 0 to 14, measuring solution acidity:
  • Acidic solutions: pH < 7
  • Neutral solutions: pH = 7
  • Basic solutions: pH > 7
• Neutralization reactions between acids and bases yield salt and water.

Atomic Number and Mass Number

• The atomic number (Z) represents the total number of protons in an atom's nucleus and is unique to each element.
• The mass number (A) is the sum of protons and neutrons in the nucleus.
• The mass number can be calculated using the formula: Mass Number = Number of Protons + Number of Neutrons.
• For example, carbon has an atomic number of 6 (6 protons) and a mass number of 12 (6 protons + 6 neutrons).

Test your knowledge of atomic structure and chemical reactions in this quiz designed for 10th-grade chemistry students. Explore the essential concepts of atoms, nuclei, electrons, and various chemical reaction types including synthesis and decomposition. Understand the conservation of mass and the differences between exothermic and endothermic reactions.