C1 Atomic structure and the periodic table

• What are all substances made of?

  Atoms
• What is the radius of an atom?

  About 0.1 nanometre
• What does the nucleus of an atom contain?

  Protons and neutrons
• What is the radius of the nucleus compared to the atom?

  About 1/10,000 of the radius of an atom
• Why does the nucleus have a positive charge?

  Because of the protons
• Where is most of the mass of an atom concentrated?

  In the nucleus
• What is the charge and relative mass of a proton?

  Charge: +1, Relative mass: 1
• What is the charge and relative mass of a neutron?

  Charge: 0, Relative mass: 1
• What is the charge and relative mass of an electron?

  Charge: -1, Relative mass: very small
• How do electrons move in an atom?

  They move around the nucleus in electron shells
• Why are atoms neutral?

  Because they have the same number of protons as electrons
• What happens in an ion?

  The number of protons does not equal the number of electrons
• What is the charge of an ion with a 2- charge?

  It has two more electrons than protons
• What does the nuclear symbol of an atom indicate?

  It tells you the atomic number and mass number
• What does the atomic number represent?

  The number of protons in the atom
• How do you calculate the number of neutrons in an atom?

  Subtract the atomic number from the mass number
• What is the atomic number of sodium?

  11
• What defines an element?

  An element is a substance made up of atoms that all have the same number of protons
• How many different elements are there approximately?

  About 100 different elements
• What do all atoms of a particular element have in common?

  They have the same number of protons
• What are isotopes?


  Different forms of the same element with the same number of protons but different numbers of neutrons
• What is an example of isotopes of carbon?

  Carbon-12 and Carbon-13
• What is relative atomic mass?

  It is the weighted average of the masses of all the isotopes of an element
• How do you calculate the relative atomic mass of an element?


  $\text{Relative atomic mass} =$$\frac{\sum (\text{isotope abundance} \times \text{isotope mass number})}{\sum \text{abundances of all isotopes}}$
• What happens when elements mix together?

  They form new substances called compounds
• What are compounds?


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

  By chemical bonds formed through giving away, taking, or sharing electrons
• What is required to separate the original elements of a compound?

  A chemical reaction
• What happens in ionic bonding?

  Metal atoms lose electrons to form positive ions, and non-metal atoms gain electrons to form negative ions
• Give an example of a compound that is bonded ionically.

  Sodium chloride
• What happens in covalent bonding?


  Atoms share electrons with each other
• Give an example of a compound that is bonded covalently.

  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 does a formula show in a compound?

  What atoms are in the compound and their proportions
• What do brackets in a formula indicate?

  The little number outside the bracket applies to everything inside the brackets
• What is the process of balancing chemical equations?

  Ensuring the same number of atoms on both sides of the equation
• What is the first step in balancing a chemical equation?

  Find an element that doesn't balance and put in a number to try and sort it out
• What is a mixture?


  A combination of different substances that are not chemically bonded
• How can the parts of a mixture be separated?

  By physical methods such as filtration, crystallization, simple distillation, fractional distillation, and chromatography
• What are the properties of a mixture?

  The properties are just a mixture of the properties of the separate parts