Atom hist,elect structure,p tab dev,metals&nonmetals,ions

• What did John Dalton describe atoms as in the early 19th century?


  Solid spheres
• What conclusion did J.J. Thomson reach about atoms in 1897?


  Atoms contain smaller, negatively charged particles called electrons
• What is the "plum pudding" model of atomic structure?

  It shows the atom as a ball of positive charge with electrons stuck in it
• Who conducted the alpha particle scattering experiments in 1909?


  Ernest Rutherford and Ernest Marsden
• What did Rutherford and Marsden expect to happen during their alpha particle scattering experiments?


  They expected the particles to pass straight through or be slightly deflected
• What did Rutherford conclude from the results of the alpha particle scattering experiments?

  The plum pudding model was incorrect; the atom has a tiny, positively charged nucleus
• What is the nuclear model of the atom proposed by Rutherford?

  It consists of a tiny, positively charged nucleus surrounded by a cloud of negative electrons
• What problem did scientists identify with Rutherford's nuclear model regarding electron behavior?

  Electrons in a cloud would be attracted to the nucleus, causing the atom to collapse
• Who proposed the idea that electrons occupy fixed shells around the nucleus?

  Niels Bohr
• What did Bohr's model suggest about the arrangement of electrons?

  Electrons orbit the nucleus in fixed shells and are not found in between
• How did Bohr's theory of atomic structure gain support?

  It was supported by many experiments and explained other scientists' observations
• What particles did further experiments by Rutherford reveal in the nucleus?

  Protons
• What did James Chadwick discover about the nucleus about 20 years later?

  He provided evidence for neutral particles called neutrons
• What is the modern accepted model of the atom called?

  The nuclear model
• What are the rules for electron shells in an atom?

  • Electrons occupy shells (energy levels).
  • Lowest energy levels fill first (closest to nucleus).
  • Maximum electrons per shell: 1st shell: 2, 2nd shell: 8, 3rd shell: 8.
  • Atoms prefer full electron shells (like noble gases).
  • Atoms with incomplete outer shells tend to react.
• What is the electronic structure of nitrogen with atomic number 7?

  2, 5
• What is the electronic structure of magnesium with atomic number 12?

  2, 8, 2
• How were elements arranged in the early 1800s?

  • By physical and chemical properties.
  • By relative atomic mass (average mass of one atom).
  • No knowledge of atomic structure (protons, neutrons, electrons).
• Who is credited with creating a more effective periodic table in 1869?

  Dmitri Mendeleev
• What did Mendeleev do differently in his periodic table compared to earlier versions?

  He left gaps for undiscovered elements and arranged elements by properties
• How did Mendeleev predict the properties of undiscovered elements?

  By leaving gaps in his table and observing patterns in properties
• What confirmed Mendeleev's approach to arranging elements in the periodic table?

  The discovery of isotopes, which have different atomic masses but similar properties
• What is the significance of the modern periodic table?

  • Elements are arranged by increasing atomic (proton) number.
  • Reveals repeating patterns in properties of elements.
  • Helps in understanding chemical behavior and relationships.
• What did Mendeleev consider when arranging elements in the periodic table?

  He considered both atomic mass and properties of the elements.
• Why do isotopes of the same element occupy the same position on the periodic table?

  Because they have the same chemical properties despite differing atomic masses.
• What is the significance of the periodic table in chemistry?

  • Organizes elements by increasing atomic number
  • Reveals repeating patterns in properties
  • Helps identify metals and non-metals
  • Aids in remembering properties of elements
• How many elements are approximately in the periodic table?

  About 100 elements.
• What does the group number in the periodic table indicate?

  The group number indicates the number of electrons in the outer shell.
• What can you predict about elements in the same group of the periodic table?

  They are likely to react in a similar way.
• How does reactivity change in Group 1 and Group 7 as you move down the groups?

  Reactivity increases in Group 1 and decreases in Group 7 as you go down.
• What are the rows in the periodic table called?

  Periods.
• What are the main characteristics of metals and non-metals in the periodic table?

  • Metals:
  • Form positive ions
  • Located on the left and bottom
  • Most elements are metals
  • Non-metals:
  • Located on the right and top
  • Do not generally form positive ions
• Why do atoms react to form ions?

  Atoms react to achieve a full outer shell of electrons.
• What type of ions do metals form when they react?

  Positive ions (cations).
• What type of ions do non-metals form when they react?

  Negative ions (anions).
• How can you determine the charge of an ion formed by an element?

  The charge is equal to the number of electrons lost or gained.
• What are the charges of ions formed by elements in Groups 1, 2, 6, and 7?

  • Group 1: 1+ ions
  • Group 2: 2+ ions
  • Group 6: 2− ions
  • Group 7: 1− ions
• What happens to a sodium atom (Na) when it forms a sodium ion (Na⁺)?

  It loses 1 electron to achieve a stable electronic structure.
• What happens to a magnesium atom (Mg) when it forms a magnesium ion (Mg²⁺)?

  It loses 2 electrons to achieve a stable electronic structure.
• What happens to a chlorine atom (Cl) when it forms a chloride ion (Cl⁻)?

  It gains 1 electron to achieve a stable electronic structure.