Putting Atoms Together

1. Putting Atoms Together

2. Review:

3. Matter is divided into 2 main groups: • Pure Substances: • Made of only 1 type of particle • Mixtures: • Made of 2 or more types of particles

4. Mixtures can be divided further: • Solutions: • Different components cannot be distinguished (they look like one substance) • Mechanical Mixtures: • Individual components can be seen, they do not mix together

5. Pure Substances can also be divided into: • Compounds: • These are substances that contain two or more different elements, in fixed proportions.

6. Pure Substances can also be divided into: • Elements: • Pure substances that cannot be broken down into simpler substances. • More importantly: They contain only one type of atom!

7. Elements: • Are the “building blocks” of all matter • Think of Lego: a small number of different blocks, but they can be combined to form anything you can think of!

8. Elements vs Compounds: • Elements are made of one type of atom. • Compounds are made of 2 or more elements. • Therefore: Compounds are made of TWO or MORE types of atoms.

9. Try This: • Determine which of the items in the list below are elements and which are compounds: H2O CO2 Ar Ag NaCl CO O2

10. Molecules • A molecule is two or more atoms that are chemically joined together. • Molecules are defined by a chemical formula, which shows the number and type of each atom in a molecule. • Example: The chemical formula for water is H2O.

11. Try This Again: • Now determine which of the items in the list below are atoms and which are molecules: H2O CO2 Ar Ag NaCl CO O2

12. Molecules (cont’d) • Can also be divided into 2 types: • Molecular Elementsand Molecular Compounds • Molecular combinations involved non metals only.

13. Molecular Elements • Let’s look at oxygen: Like an oxygen atom, oxygen gas O2 (the stuff we breathe) is an element, because it has only one type of atom. We call O2 a Molecular Element: a molecule made of atoms of the same element.

14. O2 O O

15. There are only Seven… • Elements that form molecules made of 2 atoms. We call these the diatomic molecules. • The seven diatomic molecules are: H2, O2, F2, Br2, I2, N2, Cl2 These elements are never found in nature as single atoms.

16. An easy way to remember… • If you are having trouble remembering all of those, just remember: HOFBrINCl it rhymes with Twinkle

17. Molecular Compounds • composed of more than one type of element. • Most molecules are molecular compounds. • From the chemical formula, we can determine how many atoms of each element are found in the molecule.

18. Example: Water • chemical formula is H2O • The subscript “2” tells us there are 2 hydrogen atoms. • Because the oxygen does not have a subscript, it means there is only 1 oxygen atom. • Therefore, for every water molecule, we have 2 hydrogen atoms and 1 oxygen atom.

19. Water H H O

20. Sugar • Sugar has the chemical formula C6H12O6 • From this formula, how many of each atom does sugar have? • Carbon atoms: • Hydrogen atoms: • Oxygen atoms:

21. Sugar

22. Some other Common Molecules: • Caffeine: C8H10N4O2 • Capsaicin: C18H27NO3 (this is what makes food spicy) • Vinegar: C2H4O2

23. Try This: • Figure out the Total number of atoms of the following molecules: H2SO4 CO2 NO3 KOH HCl C5H5N5O

24. Ionic Compounds • Involve combinations between a metal and a non metal. • These compounds involve charged atoms called ions. • An ion forms when a neutral atom loses or gains electrons.

25. When an atom loses electrons it becomes positive and is called a cation. • When an atom gains electrons is becomes negative and is a called an anion. Examples: Aluminum Chloride (AlCl3) Sodium Sulfide (Na2S)

26. Homework Page 261, questions # 1, 2, 3, 4