Chemical Symbols and Formulas (Press F5 to begin presentation)

Chemical Symbols We have learned that an element is a pure substance that is made up of identical atom and has definite properties Scientists developed a system that represented the elements with a symbol that was accepted world wide

Chemical Symbol Abbreviation of the name of the element, consisting of one or two letters. e.g. the symbol for oxygen is O, the symbol for carbon is C. Since C has already been used for carbon, calcium has the symbol Ca. The second letter is not capitalized. Element Symbol Origin of name Aluminum Al Latin: alumen, a bitter salt Florine F Latin: fluor, a flow Carbon C Latin: carbo, charcoal Potassium K Latin: Kalium Sodium Na Latin: Natrium

Worksheet Complete PART A of the word document “4b – Symbols and Formulas”

Chemical Formulas Combining of chemical symbols are called chemical formulas The chemical formula indicates which elements are present and how many atoms of each element are found in that substance E.g. table salt is a compound made up of the elements sodium (Na) and chlorine (Cl). The chemical formula is NaCl

Chemical Formulas If more than one atom of an element is in a compound, the symbol is followed by a small number written below the line. This number, called a subscript, tells us how many atoms of that element are present E.g. water, H2O, is a compound made up of two atoms of hydrogen and one atom of oxygen

Compounds and Molecules Atoms are seldom found alone in nature. They combine with atoms of other elements Each element is able to make a specific number of connections with other elements This is called the combining capacity Scientists gave a number value to the combining capacity of each metal and nonmetal to explain the compounds they form

How Elements Combine Rule 1: Metals combine with nonmetals in many compounds Rule 2: Write the name of the metal first and the non-metal second Rule 3: Change the ending of the nonmetal to “ide” Rule 4: Each atom has its own combining capacity Rule 5: Atoms combine so that each can fill its combining capacity

Ball and Hook Model Calcium (ball) has a combining capacity of two (2 hooks) Chlorine (ball) has a combining capacity of 1 (1 hook) If one calcium combines with only one chlorine, the calcium would be unsatisfied If a second chlorine is added, then both substances are satisfied and the formula would be CaCl2

Worksheet Complete PART B of the word document “4b – Symbols and Formulas”