1. Chemical Foundations and Elements, Atoms, and Ions

2. 4.1 Elements All chemical matters contain elements Presently 115 different known elements 88 are occurred naturally 9 elements account for the most of the compounds found in earth’s crust Elements can not broken down further Distinguish by atomic number

3. Elements and the Earth’s Crust

4. Symbols of Elements Derived from Greek, Latin and German Describe the properties of element E.g Gold – Au (Aurum –shining dawn) Sodium – Na (Natrium) Use abbreviation to simplify the written word 1 st letter must be capitalized E.gFluorineF CarbonC ZincZn IronFe PhosphorousP

5. Natural of Matter Most natural materials are mixtures of pure substances Pure substances are either elements or combination of elements called compounds Law of constant composition: a given compound always has the same composition, regardless of where it comes from E.gWater always contains 8 g of Oxygen for every 1 g of hydrogen

6. 4.3 Dalton’s Atomic Theory Elements are made of tiny particles called atoms All atoms of a given element are identical The atoms of a given are different from those of any other elements

7. 4.3 Dalton’s Atomic Theory Atoms of one element can be combine with atoms of other elements to form compounds. A given compound always has the same relative numbers and types of atoms Atoms are indivisible in chemical process. Atoms can not be created or destroyed in a chemical reactions. A Chemical reaction simply changes the way atoms are grouped together.

8. 4.4 Formulas of Compounds Compound: a substance that is composed of the atoms of two or more elements Contains exactly the same relative mass Chemical Formula: expresses the type of atoms and the number of each type of unit Short, convenient and easier to recognize

9. Rules for Writing Formulas Each atom present is represented by its element symbol The number of each type of atom is indicated by a subscript written to the right of the element symbol When only on atom of a given is present, the subscript 1 is not written

10. Writing Formulas of Compounds Write the formula for each of the following compounds, listing the elements in the order given Each molecule of a compound that has been implicated in the formation of acid rain contains one atom of sulfur and three atoms of oxygen A molecule containing six carbon atoms and six hydrogen atoms A molecule contains one aluminum atom and three chlorine atoms A compound containing equal numbers of sodium and nitrogen atoms, but three times as many oxygen atoms as nitrogen atoms

11. 4.5 – 4.6 Structure of the Atom

12. Structure of the Atom Atoms are the tiny particles that made up an element Building block of matter Contains nucleus with neutrons and protons Protected by an electron cloud

13. Electrons Thomson- Found that cathode ray consists of tiny, negatively charged particles called electrons. Electrons are emitted from electrodes made of two thin pieces of metal Many different metals may be used to make electrodes Different metals contain different electrons Cathode rays can be deflected by bringing either a magnet or an electrically charged plate near tube. This deflection depends on the strength of deflecting magnetic or electric field the size of the negative charge on the electron the mass of electron

14. Electron

15. Nucleus of the Atom Nucleus – any tiny central core in an atom where the mass of the atom is concentrated. contains the atoms positive charges Electrons move in space relatively large distance away from the nucleus.

16. Nucleus of the Atom Nucleus is composed of two kinds of particles. Protons have a mass of 1.672623 x 10 -24 g and are positive charge numbers of protons equal to number of electrons in a neutral atom. Neutrons – almost identical in mass to proton but carry no charge

17. Structure of the Atom ParticleSymbolChargeMass electrone-e- 0.0005486 amu protonp+p+ +11.007276 amu neutronnono 01.008665 amu

18. 4.7 Isotopes All atoms of the same element have the same number of protons and the same number of electrons In a free atom or neutral atom, the positive charges and negative charges always yield a net zero charge Atoms with the same number of proton but differ number of neutrons is called Isotope

19. Atomic Numbers Elements differ from one another according to the number of protons in their atoms Atomic number (Z) = the number of protons in an atom = the number of electrons in an atoms

20. Mass Number Mass number (A) = number of proton (Z) + number of neutrons (N)

21. Isotopes Atoms with identical atomic numbers but different mass number Mass number is written as a superscript on the top left Atomic number is written as a subscript on the bottom left. (The atomic number is sometimes left off since all atoms of an element always contain the same number of protons) The number of neutrons in an isotope can be calculated from A-Z Number of neutrons in an atom has little effect on the chemical properties of the atom

22. Isotope A Z X Or X - A

23. Examples Write the symbol for the magnesium atom (atomic number 12) with a mass number of 24. How many electrons and how many neutrons does this atom have? Write the symbol for the silver atom (Z = 47) that has 61 neutrons The krypton atom has 48 neutron

24. Example Given the number of protons, neutrons and electrons in the following atom 60 27 Co 37 17 Cl 201 80 Hg

25. 4.8 Development of the Periodic Table A.Creation of the Periodic table 1.Ideal example of how scientific theory comes into being 2.Random observation 3.Organization of data in ways that make sense 4.Consistent hypothesis emerges 5.Explains known facts 6.Makes predictions about unknown phenomena

26. Development of the Periodic Table Mendelee's hypothesis about organizing known chemical information 1. Met criteria for a good hypothesis 2. Listed the known elements by atomic weight 3. Grouped them together according to their chemical reactivity

27. Periodic Table Periods:the horizontal row (7) Groups: the vertical column (18) *elements in the same group have similar chemical properties. The Periodic table Group 1A – Alkali Metals Group 2A – Alkaline Metals Group 7A – Halogens Group 8A -Noble Gases

28. Physical Properties Metals: Largest category of elements; found on the left side of the periodic table (left of the heavy zigzag line) Solids (except mercury) Malleable Ductile – can be drawn into thin wires without breaking Conduct heat and electricity Nonmetals Found on the right side of the periodic table (right of the heavy zigzag line). Gases, liquids, or solids -11 of 17 nonmetals are gases, one is liquid (Br) and only five are solid at room temperature (C, P, S, Se and I) Brightly colored Brittle solids Poor conductors of heat and electricity

29. 4.8 Introduction to the Periodic Table

30. Example For each of the following elements, use the periodic table in the next slide to give the symbol and atomic number and to specify whether the element is a metal or nonmetal. Also give the named family to which the element belongs (if any) Iodine Strontium Lithium Xeon

32. 4.9 Natural States of the Elements Diatomic molecules Molecules made up to two atoms of either the same of different elements E.g O 2, N 2, H 2, CO etc… few diatomics are found to occur naturally on Earth outside of laboratories

33. 4.10 Ions Ions – charged particles resulting from the loss or gain of electron Cation – positively particles resulting from the loss of electrons Na(s)  Na + + e-(aq) Anion – negatively charge particle resulting from the gain of one or more electrons Cl(s) + e-  Cl - (aq) Polyatomic ions – charged, covalently bonded groups of atoms Charged molecules – consist of specific numbers and kinds of atoms joined together by covalent bonds in a definite way NO 3 - (aq), - OH(aq)

34. Ion Charges and the Periodic Table The charge on the ion depends on the group number Main-group metal cations: charge = group number Group IA = +1 (M 1+ ) Group IIA = +2 (M 2+ ) Group IIIA = +3 (M3+) Main group nonmetal anions: charge = group number - 8 Group VA = 5 -8 = -3 Group VIA = 6 -8 = -2 Group VIIA = 7 – 8 = -1

35. Example Determine the charge of each of the following ions and write out its symbol Magnesium Oxygen Cesium Nitrogen Bromide

36. Examples How many electrons are contained in each of the following ions? a.Fe 2+ b.Co 3+ c.S 2- d. N 3-

37. 4.11 Ionic Solid Ionic solids – cations and anions are packed together in a regular manner so that the charges cancel. Na + (aq) + Cl - (aq)  NaCl(s) Mg 2+ (aq) + 2Cl - (aq)  MgCl 2 (s)

38. Ionic Compounds

39. Example Use the pairs of ions below to give the formula for the compound containing these ions Ca 2+ and Cl - Al 3+ and S 2- Mg 2+ and N 3- K + and O 2-