Chem

• Hypothesis is a statement that can be scientifically tested
• Repeating an experiment


  Reking of on experiment-repeat (pepetition)
• Validity of an experiment

  Controlled variables should be the same
• If all particles are the same, it is called a pure substance. If particles are different, it is called a mixture
• Molecule is made up of a number of atoms but it is one particle. Molecule can live independently
• Atom


  The smallest particle of matter that has all the properties of the matter it belongs to but can't exist independently
• Single atoms can be molecules (noble gases) if they have a full valence electron shell. This is called a mono-atomic molecule
• Atoms

  • H, O, Na, Li
• Elements and compounds are pure substances
• When acids react with carbonates, they form salt, carbon dioxide, and water
• When protons and electrons are the same number, it will be classified as no charge
• The Kelvin symbol K is a unit of measurement for temperature. The Kelvin scale is an absolute scale defined such that 0K is absolute zero
• Homogeneous substances have a uniform composition, like a solution where salt and sugar are dissolved in water. Heterogeneous substances have a non-uniform composition
• Filtration is semi-permeable, allowing some substances to pass through while blocking others
• Atomic Structure Overview

  Electrons are subatomic particles with a negative charge. Protons are subatomic particles with a positive charge. Neutrons are subatomic particles with no charge. Protons and neutrons are bound in the nucleus by the strong nuclear force. Protons and neutrons have approximately the same mass, much more massive than electrons. A neutral atom must have an equal number of protons and electrons. Each element has a unique number of protons, equal to the atomic number
• Proton

  A subatomic particle with a positive charge
• Electron


  A subatomic particle with a negative charge
• The positive charge on a proton is equal in magnitude to the negative charge on an electron. As a result, a neutral atom must have an equal number of protons and electrons
• Atomic number


  The number of protons in the nuclei of any of its atoms
• Mass number


  The sum of the protons and neutrons in the atom. Also referred to as nucleon number
• Isotopes

  Atoms of the same element, containing the same number of protons, but different numbers of neutrons
• Isotopes have the same chemical properties but different physical properties such as mass, density, and radioactivity
• Unstable isotopes that decay and release radiation are called radioisotopes
• The process of emitting radiation by a substance is called radioactivity
• The three types of radiation released are alpha particles, beta particles, and gamma radiation
• The decay of a radioisotope can be represented by an equation
• Alpha Radiation


  A stream of particles, a nucleus made up of 2 protons and 2 neutrons
• Beta Radiation


  A stream of particles, high-speed electrons ejected from an atomic nucleus
• Gamma Radiation


  Very high-frequency electromagnetic waves, similar to X-rays, but carrying even more energy
• Alpha particles are represented as He
• Beta particles are represented as e
• Gamma radiation is represented by y
• Types of radioactive emission

  • Alpha
  • Beta
  • Gamma
• Types of radioactive emission

  • Alpha
  • Beta
  • Gamma
• Alpha emission

  • Symbol: He
  • Identity: Helium nucleus
  • Charge: +2
  • Mass (relative to 1 proton): 4
  • Penetration Power: Low
• Beta emission

  • Symbol: Electron
  • Identity: -1
  • Mass (relative to 1 proton): 1/1836
  • Penetration Power: Medium
• Gamma emission

  • Symbol: Y
  • Identity: Electromagnetic radiation
  • Charge: 0
  • Mass (relative to 1 proton): 0
  • Penetration Power: High
• The decay of naturally occurring uranium-238 produces thorium-234, an alpha particle and gamma radiation
• Radium-226 undergoes alpha decay by producing Radon-222
• Carbon-14 decays to produce beta particles (electrons)