Chemistry

Outline Chemistry introduction Atoms Chemical symbols

Chemistry introduction Latin meaning “earth” Composition and structure during chemical reactions. studies of various atoms, molecules, crystals in isolation or combination energy and entropy

Word 'atom' from Greek for ‘indivisible’. Small central nucleus surrounded by even smaller particles called electrons. All substances made from atoms Atoms of any element different from atoms of any other element..

Chemical symbols represent atoms of each element one or two different letters For example, iron Fe sulphur S sodium Na oxygen O

The periodic table 100 different elements chart showing all the elements vertical columns called groups each group contains elements with similar properties eight main groups group 1 - reactive metals ( sodium - Na ) group 7 - very reactive non-metals (chlorine–Cl )

Reactions and compounds New substances formed by chemical reactions. Elements react together to form compounds Atoms join to other atoms using chemical bonds. E.g. Iron and sulphur - react together to form a compound called iron sulphide sodium and oxygen react together to form sodium oxide.

Mixture of iron (grey) and sulphur (yellow) powders mixture heated in test tube chemical reaction: iron sulphide formed

Chemical bonds involve electrons from reacting atoms Electrons transferred from one atom to another One atom gives electrons: other takes electrons Electrons shared between two atoms Chemical bonds

Chemical formula chemical formula of a compound shows how many of each type of atom join together One carbon atom and two oxygen atoms combine to make carbon dioxide CO2.

Equations no atoms made or lost: joined differently mass of substances at the start (the reactants) = mass of substances at the end (the products). Balanced equations show what happens to the different atoms in reactions Word equation for the reaction: copper + oxygen → copper oxide chemical formulae: Cu + O2 → CuO - unbalanced equation Balanced symbol equation: 2Cu + O2 → 2CuO

Two atoms of copper react with two atoms of oxygen to form two molecules of copper oxide

1. The atoms in an element are: a) All the same type b) Two types joined together c) About a hundred different types 2. An atom consists of: a) An electron surrounded by a nucleus b) A nucleus containing electrons c) A nucleus surrounded by electrons 3. What is the correct chemical symbol for sodium? a) NA b) Na c) na Questions

4. What do we get when two or more different types of atom join together using chemical bonds? A mixture A compound A new element 5. What are the groups in the periodic table? A row of similar elements A column of similar elements The boxes in the table 6.What do chemical bonds involve? A nucleus moving from one atom to another Electrons being transferred from one nucleus to another Electrons being shared between two atoms

7. A unit of magnesium carbonate contains one magnesium atom, one carbon atom and three oxygen atoms. What is its chemical formula? MgC3O Mg(CO)3 MgCO3 8. Which statement about chemical reactions is correct? The mass of products equals the mass of reactants The mass of products is more than the mass of reactants The mass of products is less than the mass of reactants 9. The correct balanced equation for the reaction between magnesium and oxygen is: Mg + O ==> MgO2 Mg + O2 ==> Mg2O 2Mg + O2 ==> 2MgO