Atomic structure and the periodic table

• What are atoms?

  Atoms are the basic building blocks of all substances.
• What is the radius of an atom?

  The radius of an atom is about $0.1 \text{ nanometres} (1 \times 10^{-10} \text{ m})$.
• What are the main components of an atom?

  • Protons
  • Neutrons
  • Electrons
• Where is the nucleus located in an atom?

  The nucleus is in the middle of the atom.
• What does the nucleus contain?

  The nucleus contains protons and neutrons.
• What is the radius of the nucleus?

  The nucleus has a radius of around $1 \times 10^{-15} \text{ m}$.
• Why does the nucleus have a positive charge?

  The nucleus has a positive charge because of the protons.
• Where is most of the mass of an atom concentrated?

  Almost the whole mass of the atom is concentrated in the nucleus.
• How do electrons move in an atom?

  Electrons move around the nucleus in electron shells.
• What charge do electrons have?

  Electrons have a negative charge.
• What determines the size of an atom?

  The volume of the electrons' orbits determines the size of the atom.
• What is the mass of electrons compared to protons and neutrons?

  Electrons have virtually no mass.
• Why are atoms neutral?

  Atoms are neutral because they have the same number of protons as electrons.
• What happens in an ion regarding protons and electrons?

  In an ion, the number of protons does not equal the number of electrons.
• What does the atomic number represent?

  The atomic number tells you how many protons there are in an atom.
• How do you calculate the number of neutrons in an atom?

  To get the number of neutrons, subtract the atomic number from the mass number.
• What defines an element?

  An element is a substance made up of atoms that all have the same number of protons.
• What determines the type of atom?

  The number of protons in the nucleus decides what type of atom it is.
• How many different elements are there approximately?

  There are about 100 different elements.
• What is the relationship between atoms of a particular element?

  All the atoms of a particular element have the same number of protons.
• What are isotopes?

  Isotopes are different forms of the same element with the same number of protons but a different number of neutrons.
• What is a popular example of isotopes?

  Carbon-12 and carbon-13 are popular examples of isotopes.
• What does relative atomic mass represent?

  Relative atomic mass is an average mass taking into account the different masses and abundances of all the isotopes of an element.
• How do you calculate the relative atomic mass of an element?

  Relative atomic mass (A_r) = sum of (isotope abundance x isotope mass number) / sum of abundances of all the isotopes.
• What is the relative atomic mass of copper with isotopes Cu-63 and Cu-65?

  The relative atomic mass of copper is approximately 63.6.
• What happens when elements react?

  When elements react, atoms combine with other atoms to form compounds.
• What are compounds?

  Compounds are substances formed from two or more elements held together by chemical bonds.
• How are atoms held together in a compound?

  Atoms in a compound are held together by chemical bonds.
• What is required to separate the original elements of a compound?

  A chemical reaction is needed to separate the original elements of a compound.
• What is ionic bonding?

  Ionic bonding occurs when metal atoms lose electrons to form positive ions and non-metal atoms gain electrons to form negative ions.
• What are examples of compounds that are bonded ionically?

  Examples of ionic compounds include sodium chloride, magnesium oxide, and calcium oxide.
• What is covalent bonding?

  Covalent bonding occurs when non-metal atoms share electrons.
• What are examples of compounds that are bonded covalently?

  Examples of covalent compounds include hydrogen chloride gas, carbon monoxide, and water.
• How do the properties of a compound compare to the properties of the original elements?

  The properties of a compound are usually totally different from the properties of the original elements.
• What is the formula for carbon dioxide?

  The formula for carbon dioxide is CO₂.
• What is the formula for sulfuric acid?

  The formula for sulfuric acid is H₂SO₄.
• How are formulas for compounds constructed?

  Formulas are made up of elemental symbols in the same proportions that the elements can be found in the compound.
• What do brackets in a formula indicate?

  Brackets in a formula indicate that the little number outside applies to everything inside the brackets.
• What is the formula for calcium hydroxide?

  The formula for calcium hydroxide is Ca(OH)₂.
• How many atoms are in one particle of Na₂CO₃?

  There are 6 atoms in one particle of Na₂CO₃.