C1 - Atomic Structure and Periodic Table

• What are atoms?

  The smallest part of an element that can exist
• Give examples of chemical symbols of some elements.

  An atom of oxygen is O; sodium is Na
• How many different elements are there in the periodic table?

  About 100
• How are compounds formed?

  By chemical reactions between elements
• What does a chemical reaction involve?

  The formation of new substances and energy change
• What do compounds contain?

  Two or more elements chemically combined
• How can compounds be separated into elements?

  Only via chemical reactions
• Give examples of compounds.

  CO₂, H₂O, NaCl, etc.
• What is a mixture?

  Two or more elements or compounds NOT chemically combined
• What are the properties like for each substance in a mixture?

  Their chemical properties remain unchanged
• How can we separate mixtures? Give examples.

  Using physical processes like filtration and distillation
• How could a mixture of salt and sand be separated?

  Dissolve salt in water, filter, and crystallise
• Before the discovery of the electron, what were atoms thought to be?

  Tiny indivisible spheres
• What was Thomson's plum pudding model of the atom?

  A ball of positive charge with negative electrons embedded
• What experiments did Rutherford carry out to produce the nuclear model?

  Fired alpha particles at gold foil
• How did Niels Bohr adapt the nuclear model?

  He suggested electrons orbit nucleus at specific distances
• What particle was identified as having a positive charge in the nucleus?

  Protons
• What did James Chadwick prove the existence of within the nucleus?

  Neutrons
• What is the relative charge on each sub-atomic particle?

  Electrons -1, neutrons 0, protons +1
• Why do atoms have no overall charge?

  The number of electrons equals the number of protons
• What is an atom's atomic number?

  The number of protons it has
• What do atoms of a particular element have in common?

  They have the same number of protons
• What size are atoms?

  Tiny, with a radius of about 0.1 nm
• How big is an atom's nucleus?

  Less than 1/10,000th of that of the atom
• Where is almost all the mass of an atom found?

  In the nucleus
• What are the relative masses of each sub-atomic particle?

  Proton 1, neutron 1, electron almost zero
• What is the mass number of an atom?

  The sum of its protons and neutrons
• What is an isotope?

  Atoms of the same element with different neutrons
• What are the two numbers next to each element in the periodic table?

  Atomic number and relative atomic mass
• How do you calculate how many protons, electrons, and neutrons there are in an element?

  Atomic number = protons; neutrons = mass - protons
• What is meant by the 'relative atomic mass' of an element?

  An average value considering isotope abundance
• What is the RAM of chlorine if 75% of atoms are Cl-35 and 25% are Cl-37?

  $35.5$
• How can the electronic structure of a sodium atom (2, 8, 1) be represented in a diagram?

  Two electrons in lowest, eight in second, one in third
• What is used to arrange the order of the elements in the periodic table?

  Atomic (proton) number
• How are elements with similar properties arranged?

  In columns, known as groups
• Why is the Periodic Table so named?

  Elements with similar properties occur at regular intervals
• Why do elements in the same groups have similar properties?

  They have the same number of electrons in outer shell
• What did scientists use to arrange elements before the discovery of protons, neutrons, and electrons?

  They were placed in order of atomic weight
• What were some issues with early periodic tables?

  They were incomplete and had elements in wrong groups
• How did Mendeleev overcome some issues with early periodic tables?

  Left gaps for elements yet to be discovered