Atoms and chemical equations

• Model of an atom:

  • At the center of an atom lies the NUCLEUS, containing PROTONS and NEUTRONS.
  • ELECTRONS orbit around the nucleus in electron shells.

  A) shells

  B) nucleus

  C) electrons

  
• Atoms are the smallest part of an element that can exist.

  • Incredibly small and makes up everything in the universe
  • Composed of sub-atomic particles: protons, neutrons and electrons
  • Atoms are neutral and no overall charge for they have the same number of protons and electrons cancelling each other out.
• Sub-atomic particles' properties:

  A) positive

  B) neutral

  C) negative

  D) 1

  E) 1

  F) very small

  
• Relative Atomic Mass (RAM or Ar)

  the measure of the average mass of an atom.
• The NUCLEUS is about 1/10,000th of the atom's total size, but it holds nearly ALL the atom's mass:

  • Radius of an ATOM: 0.1nm (1 x 10-10 m)
  • Radius of a NUCLEUS: 1 x 10-14 m
• Atoms of each element is represented by a CHEMICAL SYMBOL which can be found in the PERIODIC TABLE.

  E.g. Carbon has the symbol C.

  A) mass number

  B) chemical symbol

  C) atomic number

  
• Element


  A substance made up of one type of atom.
• When atoms have different numbers of PROTONS, they're classified as DIFFERENT elements, this means the ATOMIC NUMBER determines the ELEMENT of an atom.
• • To find the number of NEUTRONS, SUBTRACT the atomic number from the mass number:

  
• ISOTOPES are different forms of the same element, having the SAME NUMBER OF PROTONS but DIFFERENT NUMBERS OF NEUTRONS.

  
• Compounds are substances that form when two or more elements react and their atoms chemically combine in fixed ratio by mass.

  • In compounds, only the ELECTRONS are involved in bond formation while the nuclei remain unchanged.
  • PROPERTIES of a compound are usually different from the original elements.

  
• FORMULAS


  represents compounds and show the elements and the number of atoms of each element in a compound.

  
• Formulation


  A mixture that has been designed as a useful product including:

  • fuels, cleaning products, paints, food, medicine, fertilisers
• Relative atomic mass - every element has a RAM


  Calculated as an average mass of all its isotopes, taking account their abundance (its how common a particular isotope is).

  
• Chemical Equation


  Used to show what happens during a chemical reaction ; the left side is the reactants and the right side is the products.
• Steps to Balance Equations:

  1. Identify the number of atoms of EACH ELEMENT on either side of the equation.
  2. ADJUST the coefficients to balance that element, which may cause another element to become unbalanced.
  3. Repeat the process, adjusting coefficients until the equation is BALANCED.
• Chemical equations are balanced, as mass cannot be lost or gained, therefore you must start and end up with the same number of each atom.
• Coefficient


  tells us the number of each substance involved in the reaction 
• the conservation of mass tells us that no atoms are lost or gained in a chemical reaction, they are just rearranged.
• mixture


  A physical combination of two or more substances that aren't chemically joined.
• molecules


  a cluster of non-metal atoms that are chemically bonded together
• There are: 6 electrons, 8 neutrons and 6 protons, with the protons and neutrons in the nucleus, with electrons in shells.

  
• Mass Number


  number of Neutrons AND Protons
• Atomic number


  Number of Protons
• The number of electrons is 18.

  
• Formula to calculate the Relative Atomic Mass:

  A) Relative Atomic Mass

  B) mass number

  C) abundance

  D) 100

  E) mass number

  F) abundance

  
• Relative mass number = ( 1) mass number x abundance + 2) mass number x abundance + .... ) / 100
• Answer the question.

  A) calcium chloride

  B) carbon dioxide

  C) water

  
• alloy


  a mixture of metals