1. On Earth, matter usually can be found as a solid, liquid, or gas. What are elements?

2. Elements and the Atomic Structure

3. Elements All matter is made elements. All matter is made elements. An element is a substance that cannot be broken down into simpler substances An element is a substance that cannot be broken down into simpler substances by physical or chemical means. Ninety-two elements occur naturally on Earth and in the stars. Ninety-two elements occur naturally on Earth and in the stars. Elements larger than 92 are man-made and radioactive.

4. Elements are Made of Atoms Each element has distinct characteristics. Each element has distinct characteristics. An atom is the smallest particle of an element that has all of the characteristics of that element. An atom is the smallest particle of an element that has all of the characteristics of that element.

5. Elements are Made of Atoms The nucleus, which is made The nucleus, which is made up of protons and neutrons, forms the center of an atom. – A proton (p + ) is a tiny particle that has mass and a positive electrical charge. – A neutron (n 0 ) is a particle with about the same mass as a proton, but it has no electrical charge. All atomic nuclei have a positive charge. All atomic nuclei have a positive charge.

6. Elements are Made of Atoms The number of protons and neutrons in different atoms varies widely. The atomic number is the number of protons in an atom’s nucleus. The atomic number is the number of protons in an atom’s nucleus. The mass number or atomic mass is the combined number of protons and neutrons, which are in the nucleus. The mass number or atomic mass is the combined number of protons and neutrons, which are in the nucleus.

7. An electron (e – ) has little mass, but it has a negative electrical charge. An electron (e – ) has little mass, but it has a negative electrical charge. Elements are Made of Atoms Surrounding the nucleus of an atom are smaller particles called electrons. Surrounding the nucleus of an atom are smaller particles called electrons. An atom has an equal number of protons and electrons which produces an atom An atom has an equal number of protons and electrons which produces an atom that has no overall charge.

8. Elements are Made of Atoms An energy level represents the area in an atom where an electron is most likely to be found.

9. Electrons in Energy Levels The number of electrons in the outermost energy level determines the chemical behavior of the different elements. The number of electrons in the outermost energy level determines the chemical behavior of the different elements. Valence electrons are the outermost electrons in an atom. Valence electrons are the outermost electrons in an atom. Elements with the same number of valence electrons have similar chemical properties. Elements with the same number of valence electrons have similar chemical properties. Group 1 has 1 valence electron, group 2 has 2, Group 1 has 1 valence electron, group 2 has 2, 13 has 3, 14 / 4, 15 / 5, 16 / 6, 17 / 7, 18 / 8. 13 has 3, 14 / 4, 15 / 5, 16 / 6, 17 / 7, 18 / 8.

10. Isotopes The number of neutrons in the nuclei of an element’s atoms can vary. The number of neutrons in the nuclei of an element’s atoms can vary. Isotopes are atoms of the same element that have different mass numbers and the same chemical properties. Isotopes are atoms of the same element that have different mass numbers and the same chemical properties.  Almost all atoms have isotopes

11. What Elements are Most Abundant?

12. Compounds A compound is a substance that is A compound is a substance that is composed of atoms of two or more different elements that are chemically combined. Most compounds have totally different properties from the elements of which they are composed. Most compounds have totally different properties from the elements of which they are composed. Chemical bonds are the forces that hold the elements together in a compound creating a state of stability. Chemical bonds are the forces that hold the elements together in a compound creating a state of stability.

13. Ions Ionic Bonds – Positive and negative ions attract each other. – An ionic bond is the attractive force between two ions of opposite charge.

14. Ionic Bonding Ions Travel Group 1 travels to group 17 Group 2 travels to group 16 Metals and non metals attract All compounds are looking to become stable with 8 valence electrons. Properties of ionic bonding Brittleness High melting points Good electrical conductivity

15. Compounds Covalent Bonds – A covalent bond is the attraction of two atoms for a shared pair of electrons that holds the atoms together.

16. Compounds – A molecule is composed of two or more atoms held together by covalent bonds.

17. Covalent Bonding Formed when non-metal atoms share valence electrons 7 + 7 =16 6 + 6 =16 Use a dot diagram to predict how an atom will share it’s valence electrons.

18. Mixtures and Solutions A mixture is a combination of two or more components that are NOT chemically combined, and retain their identities. Mixtures can be physically separated. The identities of the substances DO NOT change. A homogeneous mixture is also called a solution.

19. Mixtures Mixtures When a mixture’s components are easily recognizable, such as pizza, it is called a heterogeneous mixture. When a mixture’s components are easily recognizable, such as pizza, it is called a heterogeneous mixture. In a homogeneous mixture such as chocolate milk, the component particles cannot be distinguished, even though they still retain their original properties.

20. Mixtures Common Techniques for Separating Mixtures Distillation – separates a mixture based on boiling points of the component. Examples : saltwater crude oil into gasoline and kerosene Magnet – separates iron from other objects. Centrifuge – spins and separates according to densities.

21. Solutions A mixture that appears to be a single substance but is composed of particles of two or more substances that are distributed evenly amongst each other. A mixture that appears to be a single substance but is composed of particles of two or more substances that are distributed evenly amongst each other. A solution may be liquid, gaseous, or solid. Examples of solutions Liquid - seawater Gas - air Solid - alloys

22. Solutions Dissolving – The process in which particles of substances separate and spread evenly amongst each other. Solute – substance that is dissolved. A solute is soluble, or able to dissolve. A substance that is insoluble is unable to dissolve, forms a mixture that is not homogeneous, and therefore NOT a solution. Solvent – substance in which solute is dissolved.

23. Solubility The solubility of a solute is the amount of solute needed to make a saturated solution using a given amount of solvent at a certain temperature. The solubility of a solute is the amount of solute needed to make a saturated solution using a given amount of solvent at a certain temperature. Solubility is usually expressed in grams of solute per 100 ml of solvent (g/100ml) Solubility is usually expressed in grams of solute per 100 ml of solvent (g/100ml) Three (3) methods that affect solubility Three (3) methods that affect solubility Mixing, stirring, or shaking Mixing, stirring, or shaking Heating Heating Crushing or grinding Crushing or grinding

24. Suspension A mixture in which particles of A mixture in which particles of a material are dispersed through- out a liquid or gas but are large enough that they settle out. Particles are insoluble, so they DO NOT dissolve in the liquid or gas. Particles are insoluble, so they DO NOT dissolve in the liquid or gas. Particles can be separated using a filter. Particles can be separated using a filter. Examples: Examples: Salad dressing Salad dressing Medicines that say Medicines that say “shake well before use”

25. Colloids A mixture in which the particles are dispersed throughout but are not heavy enough to settle out. Made up of solids, liquids and gases. Examples : Mayonnaise Stick deodorant milk