chem

• Who created the first periodic table and in what year?

  Dmitri Mendeleev in 1869
• How did Mendeleev arrange the elements in his periodic table?

  By atomic mass
• What did Mendeleev do for undiscovered elements?

  He left gaps and predicted their properties
• Who discovered that elements should be arranged by atomic number?

  Henry Moseley
• What are groups in the periodic table?

  Vertical columns where elements have the same number of valence electrons
• What happens as you move across a period in the periodic table?

  The atomic number increases and elements change from metals to non-metals
• What are the alkali metals in Group 1?

  Lithium, Sodium, Potassium
• How does reactivity change in Group 1 alkali metals?

  Reactivity increases down the group
• What are the halogens in Group 7?

  Chlorine, Bromine, Iodine
• How does reactivity change in Group 7 halogens?

  Reactivity decreases down the group
• What are the noble gases in Group 0?

  Helium, Neon, Argon
• What is a characteristic of noble gases?

  They are non-reactive with full outer electron shells
• What are transition metals?

  Elements in the middle of the periodic table with variable oxidation states
• What are some properties of transition metals?

  Good conductors and often used as catalysts
• How do alkali metals react with water?

  They produce hydrogen gas and hydroxides
• What do halogens form with metals?

  Salts
• What are the characteristics of noble gases?

  Inert and used in lighting
• What is the charge of protons?

  Positively charged
• What are neutrons?

  Neutral particles in the nucleus
• What are electrons?

  Negatively charged particles orbiting the nucleus
• What are isotopes?

  Atoms of the same element with different numbers of neutrons
• How do isotopes of an element differ?

  They have different physical properties
• Who proposed the "solid sphere" model of the atom?

  John Dalton
• Who discovered the electron?

  1. J. Thomson
• What did Rutherford discover using the gold foil experiment?

  The nucleus of the atom
• Who proposed that electrons orbit the nucleus in fixed energy levels?

  Niels Bohr
• Who discovered the neutron?

  James Chadwick
• What are the types of bonding in chemistry?

  • Ionic Bonding: Between metals and non-metals; electrons are transferred.
  • Covalent Bonding: Between non-metals; electrons are shared.
  • Metallic Bonding: Between metal atoms; electrons are delocalized.
• What is an example of ionic bonding?

  NaCl (Sodium Chloride)
• What is an example of covalent bonding?

  H₂O (Water)
• What is an example of metallic bonding?

  Copper (Cu)
• How do bonding and structure relate to properties of compounds?

  • Ionic Compounds: High melting/boiling points; conduct electricity when molten/dissolved.
  • Covalent Compounds: Low melting/boiling points; do not conduct electricity.
  • Metals: Good conductors of heat/electricity; malleable and ductile.
• What are the states of matter and their characteristics?

  • Solid: Strong forces, fixed positions, low energy.
  • Liquid: Moderate forces, particles can move past each other.
  • Gas: Weak forces, particles are far apart and move freely.
• What does the conservation of mass state in a chemical reaction?

  The mass of the products equals the mass of the reactants
• What must be true about balanced equations in chemical reactions?

  The number of atoms of each element must be the same on both sides
• What is a mole?

  1. 022 × 10²³ particles
• What is molar mass?

  The mass of one mole of a substance (g/mol)
• What is the equation for calculating the amount of substance in moles?

  $n =$$\frac{mass}{Molar \, Mass}$
• What is the composition of the Earth's atmosphere?

  • Primarily nitrogen (78%) and oxygen (21%).
  • Trace amounts of argon, carbon dioxide, and water vapor.
• How did the Earth's atmosphere evolve?

  • Early atmosphere: Mostly CO₂, methane, ammonia, and water vapor.
  • Later: Photosynthesis by plants produced oxygen, reducing CO₂ levels.