Chem

• Elements within the same period have similar chemical properties due to having the same number of electrons in their outermost shell.
• The periodic table is arranged by increasing atomic number, with elements grouped into periods (horizontal rows) based on their electron configuration.
• What is a compound?

  A substance with two or more different atoms bonded
• What is the chemical formula for water?

  H2O
• How many hydrogen atoms are in one water molecule?

  Two hydrogen atoms
• What does it mean if there is no number after a chemical symbol?

  It indicates an invisible one atom
• What do chemical reactions involve regarding atoms?

  Atoms change their bonds and connections
• What is the purpose of balancing chemical equations?

  To ensure the same number of atoms on both sides
• Which atoms should you balance first in a chemical equation?

  Atoms that are only in compounds
• What is a mixture?

  A combination of elements and compounds not bonded
• What is an example of a mixture?

  Air
• How can you separate sand from water?

  Using filtration
• What does crystallization do?

  Leaves a solid dissolved in a liquid behind
• What is distillation used for?

  To separate liquids based on boiling points
• What are the three main states of matter?

  Solid, liquid, gas
• How do particles behave in a solid state?

  They vibrate around fixed positions
• What happens to particles when a substance melts?

  Energy is supplied to overcome attractions
• What do state symbols indicate in chemical equations?

  The state of substances: solid, liquid, gas, aqueous
• Who proposed the plum pudding model of the atom?

  JJ Thompson
• What did Rutherford discover about the atom?

  Atoms have a small, dense nucleus
• What did Niels Bohr contribute to atomic theory?

  Electrons exist in shells or orbitals
• What are protons and neutrons' relative charges?

  Protons are +1, neutrons are 0
• What is the atomic number of an element?

  The number of protons in the nucleus
• What happens when an atom gains or loses electrons?

  It becomes an ion
• What is the mass number of an atom?

  The total number of protons and neutrons
• What are isotopes?

  Atoms of the same element with different neutrons
• What does relative abundance refer to?

  The percentage of each isotope in a sample
• How is the average relative atomic mass calculated?

  By averaging the masses of isotopes
• How did early scientists organize the periodic table?

  By atomic weights and similar properties
• What did Dmitri Mendeleev contribute to the periodic table?

  Grouped elements by properties, predicting gaps
• How do electrons fill the shells around the nucleus?

  From the inside out, with specific limits
• What are the properties of metals in the periodic table?

  They donate electrons to achieve stability
• What happens to reactivity in group one metals as you go down the group?

  Reactivity increases down the group
• What are halogens and their outer shell configuration?

  Group seven elements with seven outer electrons
• How does reactivity change in halogens down the group?

  Reactivity decreases down the group
• What are noble gases known for?

  Being very unreactive due to full shells
• What charge do metals form when they lose electrons?

  Positive ions
• What charge do group one metals form when they ionize?

  One plus ions
• What charge do group two metals form when they ionize?

  Two plus ions
• What charge do group seven nonmetals form when they gain electrons?

  Minus one ions