Elements and Compounds

• The symbols for elements are derived from their English or Latin names, or from their atomic number.
• There are currently 118 elements that have been discovered, 94 of which are naturally occurring.
• The remaining 23 elements only exist under laboratory conditions.
• An element is a substance that is made of only one type of atom.
• Elements are the simplest substances in the universe.
• Helium is an element made up of helium atoms only.
• Carbon is an element made up of carbon atoms only.
• Copper is an element made up of copper atoms only.
• Each element can be represented by a symbol.
• For many elements, the symbol is the start of the name, for example H = hydrogen or Li = lithium.
• Some of the symbols for elements are unexpected, for example Pb = lead.
• Elements and their symbols are fundamental concepts in chemistry.
• Understanding why scientists use symbols for elements is a desirable aspect of upper-level chemistry.
• Chemists use symbols to represent elements in a shorter, concise manner and to help write chemical equations.
• The first letter of an element’s symbol is always a capital letter, for example N (not n) for nitrogen.
• If there are two letters in the element’s symbol, the second letter is always a small letter, for example Co (not CO) for cobalt.
• A compound is formed when two or more atoms chemically combine to form a new substance with different properties than the original atoms.
• Magnesium oxide is a compound of magnesium and oxygen.
• Calcium sulfide is a compound of calcium and sulfur.
• Sodium chloride is a compound of sodium, chlorine and carbon.
• Copper carbonate is a compound of copper, oxygen and carbon
• Aluminium sulfate is represented as Al2(SO4)3.
• Potassium iodide is represented as KI.
• Copper sulfate is represented as CuSO4.
• Lead bromide is represented as PbBr2.
• Barium nitrate is represented as Ba(NO3)2.
• Iron carbonate is represented as FeCO3.
• Naming simple compounds of metals and non-metals involves writing down the name of the metal and the name of the non-metal, changing the ending of the word to “-ide”.
• Examples of compounds of metals and non-metals include: Iron sulfide, Magnesium nitride, Sodium chloride, Aluminium bromide.
• Naming simple compounds of metals, one non-metals and oxygen involves writing down the name of the metal, the name of the non-metal, changing the ending of the word to “-ate”.
• Examples of compounds of metals, one non-metals and oxygen include: Carbonate, Chlorate, Sulfate, Nitrate.
• Nitrogen dioxide is a compound with one atom of nitrogen and two atoms of oxygen.
• Sulfur trioxide is a compound with one atom of sulfur and three atoms of oxygen.
• Carbon dioxide is a compound with one atom of carbon and two atoms of oxygen.
• To name compounds made up of non-metals and oxygen, follow the rules: Write the name of the non-metal followed by Monoxide if there is one oxygen atom, Dioxide if there are two oxygen atoms, or Trioxide if there are three oxygen atoms.
• Calcium nitrate contains the elements calcium, nitrogen and oxygen
• Carbon trioxide is a compound with one atom of carbon and three atoms of oxygen.
• The elements and their respective numbers in a compound can be determined by looking at the chemical formula.