Chemistry Chapter 4: Atomic Structure Flashcards

Democritus's Atomic Theory

• Matter consists of empty space allowing atom movement.
• Atoms are solid, homogeneous, indestructible, and indivisible.
• Varying shapes and sizes of atoms account for different matter properties.

Dalton's Atomic Theory

• All matter is made of tiny atoms.
• Atoms of an element are identical in size and mass; different elements have different atoms.
• Atoms cannot be created, divided, or destroyed.
• Atoms combine in simple whole-number ratios to form compounds.
• During chemical reactions, atoms are rearranged.

Limitations of Dalton's Theory

• Recognizes that atoms have slightly different masses and are divisible into subatomic particles.

Atom Definition

• The smallest particle of an element which retains its chemical identity.

Cathode Ray

• A beam of electrons produced by the cathode in an electrical discharge tube.

Cathode

• The negatively charged electrode from which electrons are emitted.

Anode

• The positively charged electrode through which electrons exit the device.

Electron

• A negatively charged particle located outside the atomic nucleus.

Robert Milikan

• Known for measuring the charge of the electron.

J.J. Thomson

• Discovered electrons in 1897 using cathode rays and positively charged plates; proposed the "plum pudding model."

Mass of an Electron

• Approximately 1/1840 of a proton's mass.

Plum Pudding Model

• Suggests electrons are spread within a uniform positive charge.

Rutherford's Nuclear Atomic Model

• Based on gold foil experiment results; alpha particles mostly pass through with minor deflections.
• Identified a dense positive nucleus responsible for deflections of alpha particles.

Proton

• A subatomic particle with a positive charge, essential to atomic structure, discovered by Rutherford.

Mass of a Proton

• Proton's mass is approximately 1 atomic mass unit (amu).

Neutron

• A subatomic particle with no electrical charge, identical mass to a proton.

Electron Cloud

• A probability region around an atomic nucleus where electrons are likely found.

Atomic Number

• Indicates the number of protons in an atom's nucleus, determining the element's identity.

Mass Number

• Total count of protons and neutrons in an atomic nucleus.

Isotopes

• Variations of the same element differing in neutron count.

Average Atomic Mass

• A weighted average reflecting the atomic mass of isotopes based on their abundance.

Atomic Mass Unit (amu)

• Defined as one-twelfth the mass of a carbon-12 atom.

Atomic Mass

• The average of the mass numbers of an element's isotopes.

Nuclear Reactions

• Involve splitting or fusing atomic nuclei, producing significant energy compared to chemical reactions.

Radioactivity

• The spontaneous emission of radiation from certain substances.

Radiation

• Energy emitted in the form of rays, waves, or particles.

Radioactive Decay

• The release of nuclear particles and energy from unstable atomic nuclei.

Alpha Radiation

• Composed of alpha particles, deflected toward a negatively charged plate in electric fields.

Alpha Particles

• Formed from two protons and two neutrons; equivalent to a helium-4 nucleus.

Alpha Particle Properties

• Largest radioactive particle with limited range; most damaging due to mass.

Nuclear Equations

• Represent changes involving atomic and mass numbers in radioactive processes.

Beta Radiation

• Involves the emissions of beta particles during decay.

Beta Particles

• Electrons emitted from neutron decay; low mass and charge of -1, moderate penetrating power.

Effects of Alpha Particle Emission

• Results in a decrease of mass number by 4 and atomic number by 2.

Conservation in Nuclear Equations

• Mass numbers and atomic numbers must balance on both sides of the equation.

Beta Decay Process

• A neutron converts into a proton and emits an electron, leaving the mass number unchanged while increasing the atomic number by 1.

Transmutation

• The transformation of one element into another via radioactive decay.

Chemical vs. Nuclear Reactions

• Chemical reactions affect electron arrangements; nuclear reactions involve changes in the atomic nucleus.

Gamma Rays

• High-energy electromagnetic radiation with no mass or charge; highly penetrating and not deflected in fields.