what is an atom?

• What are atoms constructed from?

  Fundamental particles
• What do atoms make up in the world around us?

  All matter
• How do atoms compare to Lego blocks?

  They remain unchanged when models change
• What are materials made of only one sort of atom called?

  Elements
• What are materials made of different kinds of atoms called?

  Compounds
• What is the symbol for hydrogen?

  H
• Why do some element symbols differ from their names?

  Derived from other languages
• What is the symbol for lead?

  Pb
• Who constructed the periodic table?

  Dmitri Mendeleev
• How did Mendeleev arrange the elements?

  By increasing atomic mass
• What did Mendeleev's periodic table help identify?

  Gaps for undiscovered elements
• What is considered the last stable atom?

  Bismuth
• What are the names of the particles that make up atoms?

  Protons, neutrons, and electrons
• Where do protons and neutrons reside in an atom?

  In the nucleus
• What is the mass of an electron compared to a neutron or proton?

  About 1,000th of their mass
• What is the effective mass of an electron considered to be?

  Essentially zero
• How do we define elements?

  By the number of protons
• What must be equal in a neutral atom?

  Number of protons and electrons
• What charge do protons have?

  Positive charge
• What charge do electrons have?

  Negative charge
• What are charged atoms called?

  Ions
• What is the role of neutrons in the nucleus?

  Bind protons together
• What are isotopes?

  Atoms with different neutron numbers
• How do isotopes differ from each other?

  By their mass
• What happens if there are too many neutrons in a nucleus?

  It becomes unstable and may split
• What is radioactivity?

  Unstable atoms splitting into smaller atoms
• What should you remember about electrons?

  They are essentially massless
• What charges do protons and electrons have?

  Protons are positive, electrons negative
• What is the charge of neutrons?

  No charge