Chem for Grade 7.docx

Chemistry Basics  Atom  Smallest particle that all matter is made of  Comprised of a nucleus (in center) and electron shells (orbit the nucleus)  Atoms contain 3 subatomic particles- protons, neutrons, electrons  Protons (positively charged) and Neutrons (neutral) are located in the nucleus  Electro...

Chemistry Basics  Atom  Smallest particle that all matter is made of  Comprised of a nucleus (in center) and electron shells (orbit the nucleus)  Atoms contain 3 subatomic particles- protons, neutrons, electrons  Protons (positively charged) and Neutrons (neutral) are located in the nucleus  Electrons (negatively charged) orbit the nucleus in electron shells  Electron shell maximum electron capacity  1st shell = 2  2nd shell = 8   3rd shell = 18 (stable at 8)  4th shell = 32   Element  Consist of the same type of atom  Elements are the building blocks from which all substances are made  They are listed in the Periodic Table in order according to the number of protons in the nucleus. This is known as the atomic number.  Each has its own symbol. Examples: Hydrogen H, Carbon C, Nitrogen N, silver Ag, Lead PB, Mercury Hg.  Molecule  More than one atom joined together by a chemical bond  If they are the same type of atom= molecule of element (eg.O2), different atoms= molecule of compound (eg. CO2)  Compound  When 2 or more different types of atoms are bonded together  Common examples: water H2O, carbon dioxide CO2, methane CH4, glucose C6H12O6  The formula tells us how many atoms from each element are present. Eg. CO2 = 1 carbon atom and 2 oxygen atoms  Mixture  Can be comprised of atoms, elements and compounds in varying quantities  No formula can be written  Mixtures can be separated by physical means using separation techniques  Examples: salt water, air, soft drink, perfume  Periodic Table  The rows are called periods and columns are called groups  Metals are found on the left and non-metals to the right. The group that divides them are the metalloids.  The information provided for each element includes: Atomic number, symbol, name and atomic mass.  Atomic Number = The number of protons in an atom = The number of electrons in an atom  Atomic Mass = How heavy the nucleus is. This is equal to the number of protons + the number of neutrons.