1. NOTES: 2.1 – The Nature of Matter

2. Key Questions: Identify the three subatomic particles found in atoms. Explain how all of the isotopes of an element are similar and how they are different. Explain how compounds are different from their component elements. Describe the two main types of chemical bonds

3. What makes up all matter? A chemical element is a pure substance that consists of just one type of atom. Atoms are the basic unit of matter. The atom is the smallest unit which retains all of the physical and chemical properties of its element.

5. Chem ical Compound - A substance formed by the chemical combination of two or more elements in a fixed proportion. The properties of the compound are usually very different from the elements that make up the compound.

6. Examples of Compounds Water - H 2 O Salt – NaCl Methane – CH 4 Titanium Dioxide – TiO 2

7. Examples of Compounds

8. Properties of Elements

9. Three Subatomic Particles ParticleChargeLocationMass Proton (+)Nucleus1.0007 amu Neutron NeutralNucleus1.0008 amu Electron (-) Orbiting nucleus 0.0005 amu

10. Atomic Number – -the number of protons in an atom of an element all atoms of an element have the same atomic # written as a subscript next to the element’s symbol in a neutral atom, the number of protons is equal to the number of electrons (balanced charges).

11. Mass Number – -the number of protons and neutrons in an atom of an element. The number of neutrons may vary, but the proton number remains constant. Written as a subscript next to the element’s symbol

12. Isotopes- -Atoms of an element that have more or fewer neutrons.

13. Isotopes- in nature, elements occur as mixtures of isotopes. some are radioactive: unstable isotope where nucleus decays emitting sub-atomic particles and/or energy

14. Half-Life the time it takes for half the nuclei in a radioactive isotope sample to decay

15. Energy Level of Electrons

16. Chemical Bonding Covalent Bond – strong chemical bond between atoms formed by electrons being shared by the atoms.

17. Ionic Bond – bond formed by the attraction of a positive ion to a negative ion Anion – positive ion Cation – negative ion

18. Chemical Reactions bonds between atoms are formed or broken, causing substances to combine and recombine as different molecules CH 4 + O 2 CO 2 + H 2 O

19. All of the chemical reactions that occur within an organism are referred to as that organism’s metabolism Chemical Reactions

20. Reactants: the substance(s) at the beginning of a reaction; shown on the left side of the equation Products: the substance(s) at the end of a reaction; shown on the right side of the equation. Chemical Reactions CH 4 + O 2 CO 2 + H 2 O