Atomic Structure & Electronic Configurations

• What are the key terms related to materials and chemical properties?

  • Atom
  • Ion
  • Element
  • Compound
  • Molecule
  • Mixture
  • Mass number / Atomic mass
  • Atomic number
  • Group
  • Period
  • Orbitals
• What is an element?

  An element has only one type of atom and cannot be decomposed in a chemical reaction.
• What is a compound?

  A compound is made of two or more atoms chemically bonded together.
• What is a mixture?

  A mixture is made of atoms or molecules that are NOT chemically bonded together.
• What is an atom?

  An atom is the smallest particle of an element that can take part in a chemical reaction.
• What is a molecule?

  A molecule is a group of atoms bonded together, representing the smallest unit of a chemical compound.
• What are the fundamental particles of an atom?

  • Protons
  • Neutrons
  • Electrons
• What is the charge of a proton?

  +1
• What is the charge of a neutron?

  0
• How do you calculate the mass of a carbon-12 atom?

  By adding the masses of its protons and neutrons.
• If a carbon-12 atom has 6 protons, 6 neutrons, and 6 electrons, what is its mass?

  12 (using relative masses)
• What is the atomic number?

  The atomic number is the number of protons in the nucleus of an atom.
• What is the mass number?

  The mass number is the sum of the protons and neutrons in the nucleus.
• How do you find the number of neutrons in an atom?

  By subtracting the atomic number from the mass number.
• What is the relationship between protons and electrons in an atom?

  Any atom contains equal numbers of protons and electrons.
• What is the nucleus of an atom?

  The nucleus is the central part of an atom composed of protons and neutrons.
• What is a proton?

  A proton is a positively charged particle found within an atomic nucleus.
• What is a neutron?

  A neutron is an uncharged particle found within an atomic nucleus.
• What is an electron?

  An electron is a negatively charged particle located in shells that surround an atom's nucleus.
• What is the significance of the atomic number (Z)?

  The atomic number indicates the number of protons in the nucleus of an atom.
• What is the significance of the mass number (A)?

  The mass number is the sum of the protons and neutrons in the nucleus of an atom.
• If sodium (Na) has a mass number of 23 and an atomic number of 11, how many neutrons does it have?

  12 neutrons
• What is the relationship between atomic number and mass number?

  • Atomic Number (Z): Number of protons
  • Mass Number (A): Sum of protons and neutrons
• What are isotopes?

  • Atoms with the same atomic number but different mass numbers
  • Same number of protons but different numbers of neutrons
• What are the properties of isotopes?

  • Chemical properties are identical
  • Physical properties (like density) can differ
• What is relative molecular mass?


  • Mass of a molecule relative to the 12C isotope
  • Used for compounds like CO2 and N2
• What is relative formula mass?


  • Similar to relative molecular mass
  • Used for any formula of a species or ion
• What is the Aufbau principle?


  • Electrons fill orbitals starting from the lowest energy level
  • Important for determining electronic configurations
• What is the significance of electronic configurations?


  • Determines the arrangement of electrons in an atom
  • Influences chemical properties and reactivity
• What is the Bohr model of the atom?


  • Describes the atom as a small nucleus of protons and neutrons
  • Electrons circulate around the nucleus in defined shells
• What should students know before studying electronic configurations?

  • Electrons are found outside the nucleus in energy levels (shells)
  • Electronic configurations of the first 20 elements in 2,8,1 notation
• What does the Aufbau principle state?


  Electrons enter the lowest available energy level.
• How can you deduce the electronic configuration of an atom?


  By knowing the atomic number and ionic charge.
• What is the significance of ionization energy in terms of reactivity?


  It explains trends in reactivity of elements.
• What are the main components of electronic configurations?

  • The Bohr Atom
  • Levels and sub-levels
  • Rules and principles
  • Orbitals
  • Rules for filling orbitals
• What did the Bohr theory propose about the structure of the atom?


  It proposed a small nucleus of protons and neutrons surrounded by circulating electrons.
• What is the maximum number of electrons that can be held in the first shell?


  2 electrons
• What is the maximum number of electrons that can be held in the second shell?


  8 electrons
• What is the maximum number of electrons that can be held in the third shell?


  18 electrons
• What is the maximum number of electrons that can be held in the fourth shell?


  32 electrons