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Questions and Answers
Which of the following is NOT a property of compounds?
Which of the following is NOT a property of compounds?
- Compounds are composed of two or more elements.
- Compounds are always homogeneous mixtures. (correct)
- Compounds can be chemically broken down into simpler substances.
- Compounds have a fixed definite proportion of elements.
What is the defining characteristic of an element?
What is the defining characteristic of an element?
- The number of neutrons in its atoms.
- The mass of its atoms.
- The number of electrons in its atoms.
- The number of protons in its atoms. (correct)
Which of the following statements accurately describes isotopes?
Which of the following statements accurately describes isotopes?
- Isotopes are atoms of different elements with the same number of protons and neutrons but a different number of electrons.
- Isotopes are atoms of the same element with the same number of protons and neutrons but a different number of electrons.
- Isotopes are atoms of the same element with the same number of protons and electrons but a different number of neutrons. (correct)
- Isotopes are atoms of different elements with the same number of protons and electrons but a different number of neutrons.
What is the significance of the 'A' value in the notation 'X-A' for isotopes?
What is the significance of the 'A' value in the notation 'X-A' for isotopes?
Which of the following best describes the difference between an element and a compound?
Which of the following best describes the difference between an element and a compound?
What is the significance of Avogadro’s Number?
What is the significance of Avogadro’s Number?
Which statement correctly describes cations?
Which statement correctly describes cations?
How is the molar mass of an element related to its atomic mass?
How is the molar mass of an element related to its atomic mass?
What occurs when an atom gains electrons?
What occurs when an atom gains electrons?
Which of the following describes natural abundances of isotopes?
Which of the following describes natural abundances of isotopes?
Flashcards
Element
Element
A substance that cannot be chemically broken down and is made up of a single type of atom.
Compound
Compound
A substance made of two or more elements combined in fixed proportions.
Subatomic Particles
Subatomic Particles
The smaller particles that make up all atoms: protons, neutrons, and electrons.
Protons
Protons
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Isotopes
Isotopes
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Atomic Mass
Atomic Mass
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Ions
Ions
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Cations
Cations
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Anions
Anions
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Avogadro's Number
Avogadro's Number
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Study Notes
Elements and Compounds
- Elements are substances that cannot be broken down into simpler substances.
- They are the basic building blocks of matter.
- Elements are composed of single types of atoms (e.g., helium).
- Compounds are substances composed of two or more elements in fixed proportions.
- Most elements combine with other elements to form compounds (e.g., water, sugar).
Dalton's Atomic Theory (1808)
- Elements are composed of tiny particles called atoms.
- All atoms of a given element are identical.
- Elements are different from each other.
- Atoms cannot be changed into different atoms (created or destroyed) during chemical reactions.
- Compounds are formed when atoms of more than one element combine. A specific compound always has a fixed, consistent ratio of atoms of each element.
Subatomic Particles
- All atoms are composed of the same subatomic particles:
- Protons (positive charge)
- Neutrons (no charge)
- Electrons (negative charge)
- The charges of protons and electrons are equal but opposite.
- Neutrons have no charge.
Isotopes
- Atoms of the same element can have different numbers of neutrons.
- These are called isotopes.
- Isotopes have the same number of protons but different numbers of neutrons.
- Mass number is the sum of protons and neutrons in an atom.
- Atomic number is the number of protons in an atom (or number of electrons in a neutral atom).
Atomic Mass
- Natural abundances refer to the percentage of a given element's different isotopes in a naturally occurring sample.
- The atomic mass of an element reflects the average mass of its isotopes, weighted by their fractional abundance.
- Calculation: ∑(fraction of isotope n) × (mass of isotope n)
Ions
- Atoms can gain or lose electrons to become charged particles called ions.
- Positively charged ions are called cations.
- Negatively charged ions are called anions.
Avogadro's Number
- A mole (mol) is the amount of a substance containing 6.02214 × 1023 pieces (atoms, molecules, or other particles).
Molar Mass
- Molar mass is the mass of one mole of a substance.
- For elements, the molar mass in grams per mole is numerically equal to the element's atomic mass in atomic mass units (amu).
- To convert between mass and number of atoms/molecules, use Avogadro's number as a conversion factor.
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