Chemistry Basics: Elements, Atoms, and Molecules
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Questions and Answers

What is the correct way to represent the ionic compound formed between magnesium and chloride?

  • Mg2Cl2
  • MgCl
  • Mg2Cl
  • MgCl2 (correct)

    • Which of the following correctly shows the valency of silver?

  • 1+ (correct)
  • 3+
  • 2+
  • 4+

    • How should the formula for ammonium hydroxide be written?

  • N2H4O
  • NH4OH (correct)
  • NH4O
  • NH3OH

    • Which of the following ions has a valency of 2+?

    <p>Zinc</p> Signup and view all the answers

    What is the proper representation for the ionic bond between calcium and oxide?

    <p>CaO</p> Signup and view all the answers

    What is the atomicity of oxygen?

    <p>2</p> Signup and view all the answers

    Which of the following represents a diatomic molecule?

    <p>Oxygen</p> Signup and view all the answers

    Which compound is formed by the elements nitrogen and hydrogen?

    <p>Ammonia</p> Signup and view all the answers

    What is the combining capacity of an element called?

    <p>Valency</p> Signup and view all the answers

    What kind of ion is formed when an atom loses electrons?

    <p>Cation</p> Signup and view all the answers

    Which element has an atomicity of 4?

    <p>Phosphorus</p> Signup and view all the answers

    What type of molecules do compounds formed from metal and non-metal elements contain?

    <p>Ions</p> Signup and view all the answers

    What is the molecular composition of hydrochloric acid?

    <p>H and Cl</p> Signup and view all the answers

    What is the correct symbol for Aluminium?

    <p>Al</p> Signup and view all the answers

    Which element has an atomic mass of 32 u?

    <p>Sulphur</p> Signup and view all the answers

    What defines the atomic mass of an element?

    <p>It is based on the carbon-12 atom.</p> Signup and view all the answers

    Which molecule is considered a molecule of an element?

    <p>O2</p> Signup and view all the answers

    Which of the following atomic symbols is written incorrectly?

    <p>sUl</p> Signup and view all the answers

    How is the atomic mass unit (u) defined?

    <p>As 1/12th the mass of a carbon-12 atom.</p> Signup and view all the answers

    Which of the following statements about molecules is true?

    <p>Molecules can exist independently and maintain all properties of the substance.</p> Signup and view all the answers

    What is the atomic mass of Oxygen?

    <p>16 u</p> Signup and view all the answers

    What is the formula for Calcium hydroxide?

    <p>Ca(OH)2</p> Signup and view all the answers

    Which element’s atomic mass is 14 u?

    <p>Nitrogen</p> Signup and view all the answers

    What is the molecular mass of water (H2O)?

    <p>18 u</p> Signup and view all the answers

    Which of the following combines to form Magnesium chloride?

    <p>Mg and Cl</p> Signup and view all the answers

    What does one mole of a substance equal?

    <p>6.022 x 10^23 molecules</p> Signup and view all the answers

    What is the formula for Carbon tetrachloride?

    <p>CCl4</p> Signup and view all the answers

    What is the valency of sulphide in the formula of hydrogen sulphide (H2S)?

    <p>2</p> Signup and view all the answers

    What does the law of conservation of mass state?

    <p>The sum of the masses of reactants and products remains unchanged.</p> Signup and view all the answers

    Which of these is the formula for Sodium nitrate?

    <p>NaNO3</p> Signup and view all the answers

    According to the law of constant proportions, what can be said about water?

    <p>It is composed of hydrogen and oxygen in a consistent mass ratio.</p> Signup and view all the answers

    Which of the following statements is NOT part of Dalton's atomic theory?

    <p>Atoms of a given element are always different in mass.</p> Signup and view all the answers

    What defines an atom?

    <p>A particle that can exist independently and retain chemical properties.</p> Signup and view all the answers

    What is the atomic radius of a hydrogen atom in meters?

    <p>$10^{-10}$ m</p> Signup and view all the answers

    How are the symbols of elements represented?

    <p>Symbols are often derived from the element's name or Latin name.</p> Signup and view all the answers

    Which of the following is a correct statement about atoms?

    <p>Atoms can be subdivided into protons, neutrons, and electrons.</p> Signup and view all the answers

    What happens when sodium sulfate reacts with barium chloride according to the law of conservation of mass?

    <p>The sum of the masses remains unchanged despite the reaction.</p> Signup and view all the answers

    Study Notes

    Symbol and Element

    • Elements are represented by symbols.
    • Single letter symbols are capitalized.
    • Two letter symbols are capitalized with the first letter capitalized and the second letter lowercase.

    Atomic Mass

    • The mass of an atom is compared to the mass of a carbon-12 atom.
    • One atomic mass unit (u) is 1/12th the mass of a carbon-12 atom.
    • The atomic mass of an element is the average mass of one atom compared to 1/12th the mass of a carbon-12 atom.

    Molecule

    • A molecule is the smallest particle of an element or compound that exists independently and shows all the properties of that substance.
    • A molecule can consist of two or more atoms.
    • Atomicity is the the number of atoms present in one molecule.
    • Molecules of elements can contain one or more atoms of the same element.
    • Molecules of compounds contain two or more atoms of different elements.

    Ions

    • Ions are charged particles.
    • Cations are positively charged ions.
    • Anions are negatively charged ions.
    • Valency is the combining capacity of an element.

    Laws of Chemical Combination

    • Law of Conservation of Mass: Mass cannot be created or destroyed in a chemical reaction. The total mass of reactants equals the total mass of products.
    • Law of Constant Proportions: Elements in a compound are always present in a definite proportion by mass.

    Dalton's Atomic Theory

    • Matter is made up of tiny particles called atoms.
    • Atoms are indivisible and cannot be created or destroyed in a chemical reaction.
    • Atoms of a given element are similar in mass and properties.
    • Atoms of different elements have different masses and properties.
    • Atoms combine in small whole number ratios to form compounds.
    • In a given compound, the relative number and kind of atoms are constant.

    Atom

    • An atom is the smallest particle of an element.
    • The atomic radius is measured in nanometers (nm).

    Writing Chemical Formulae

    • Place the symbol of the metal or positive ion on the left.
    • Place the symbol or formula of the non-metal or negative ion on the right.
    • Write the valencies below the symbols.
    • Cross over the valencies.
    • Polyatomic ions should be enclosed in brackets before writing the formula.

    Molecular Mass and Formula Unit Mass

    • The molecular mass is the sum of the atomic masses of all the atoms in a molecule.
    • Molecular mass is expressed in atomic mass units (u).

    Mole Concept

    • A mole of a substance contains 6.022 x 10^23 particles (atoms, molecules, or ions).
    • This number is called Avogadro's Number or Avogadro's Constant.
    • A mole represents a definite mass of a substance equal to the gram atomic mass of an element or the gram molecular mass of a compound.
    • Gram atomic mass is the atomic mass expressed in grams.

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    Lesson 2-Atoms and Molecules PDF

    Description

    This quiz covers fundamental concepts in chemistry, including atomic mass, molecular structure, and the characteristics of ions. Test your understanding of how elements are represented by symbols and the differences between cations and anions. Perfect for students looking to solidify their knowledge of introductory chemistry.

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