y9 chemistry

• Protons


  Are positively charged and are found inside the nucleus
• Neutrons


  Have no charge and are found inside the nucleus
• Electrons


  Are negatively charged and are found whizzing around outside the nucleus
• An atom is made of 3 subatomic particles named protons, neutrons and an electron
• Periodic table


  A tabular arrangement of the chemical elements, organised on the basis of their atomic number electron configurations and chemical properties
• Groups


  • The elements in the periodic table are arranged into groups
  • The groups are arranged in columns
  • The groups are numbered from 1-18
  • Elements in the same group have the same number of valence (outer shell) electrons
• Periods


  • The elements in the periodic table are arranged into periods
  • The periods are arranged in rows
  • The periods are numbered from 1-7
  • All elements in the same period have the same number of electron shells
• Atomic number


  The number of protons in the nucleus. As an atom is neutral, the number of electrons is the same as the number of protons.
• Mass number


  The total number of protons and neutrons in the nucleus. To find the number of neutrons we subtract the atomic number from the rounded mass number.
• Chemical symbol


  The chemical symbol of an element is represented using either one or two letters. The first letter is always a capital.
• Electron shells & Energy levels

  • Electrons are arranged in different shells around the nucleus
  • The innermost shell (lowest energy level) is filled first
  • Each succeeding shell can only hold a certain number of electrons before it becomes full
  • Maximum capacity of the first four shells: Shell 1 (2), Shell 2 (8), Shell 3 (8), Shell 4 (18)
• Atom


  Electrically neutral (have no charge) because they contain an equal amount of protons (+) and electrons (-)
• Ion


  An atom that has lost or gained electrons, and therefore has a charge
• Cation


  A positively charged ion formed when an atom loses electrons
• Anion


  A negatively charged ion formed when an atom gains electrons
• ductile

  can be strecthed
• malleable

  can be pounded into thin sheets
• brittle


  breaks easily
• Science has come along way since Aristotle's theory of Air, Water, Fire, and Earth
• Scientists have identified 90 naturally occurring elements, and created about 28 others
• The most abundant element in the earth's crust is oxygen
• Periodic Table


  • Organizes the elements in a particular way
  • A great deal of information about an element can be gathered from its position in the period table
  • You can predict with reasonably good accuracy the physical and chemical properties of the element
  • You can predict what other elements a particular element will react with chemically
  • Understanding the organization and plan of the periodic table will help you obtain basic information about each of the 118 known elements
• Atomic number


  How many protons an atom of that element has
• No two elements have the same atomic number
• What's in a periodic table square

  • atomic number
  • symbol
  • atomic mass
  • number of valence electrons
  • state of matter at room temperature
• Atomic Mass


  The "weight" of the atom, derived by adding the number of protons with the number of neutrons
• Isotopes


  • Atoms that have more or less neutrons than protons
• Valence electrons


  The electrons in the outer energy level of an atom that are transferred or shared when atoms bond together
• Properties of Metals


  • Good conductors of heat and electricity
  • Shiny
  • Ductile (can be stretched into thin wires)
  • Malleable (can be pounded into thin sheets)
  • Reaction with water results in corrosion
• Properties of Non-Metals


  • Poor conductors of heat and electricity
  • Not ductile or malleable
  • Solid non-metals are brittle and break easily
  • Dull
  • Many are gases
• Properties of Metalloids


  • Have properties of both metals and non-metals
  • Solids that can be shiny or dull
  • Conduct heat and electricity better than non-metals but not as well as metals
  • Ductile and malleable
• Groups


  Columns of elements with similar but not identical properties
• Periods


  Horizontal rows of elements where the properties change greatly across the row
• Hydrogen


  • Sits atop Family AI but is not a member
  • A gas at room temperature
  • Has one proton and one electron in its one and only energy level
  • Only needs 2 electrons to fill up its valence shell
• Alkali Metals


  • Found in the first column of the periodic table
  • Atoms have a single electron in their outermost level (1 valence electron)
  • Shiny, have the consistency of clay, and are easily cut with a knife
  • The most reactive metals
  • React violently with water
  • Never found as free elements in nature, always bonded with another element
• Matter


  All matter is composed of atoms and groups of atoms bonded together, called molecules
• Types of substances


  • Pure substances
  • Compounds
  • Mixtures
• Sodium and chlorine bond

  They make the compound sodium chloride known as table salt
• Compounds have different properties than the elements that make them up
• Hydrogen and oxygen bond


  They make the compound water