Unit 1 Matter and Bonding

CHEMISTRY Why do I have to study chemistry?

Atomic Theory All elements are composed of atoms Each element contains similar atoms Atoms of one element are different from ones from another Two or more different atoms bond together to form a compound

Subatomic Particles ParticleSymbol Charge Relative Mass (u) Electron e - -1 ~0 Proton p Neutron n0 1

Location of Subatomic Particles m electrons protons neutrons m nucleus

Characteristics of Electrons Extremely small mass Located outside the nucleus Moving at extremely high speeds in defined areas around the nucleus called orbitals Have specific energy levels In a neutral atom t he # of electrons equals the # of protons

Elements Are pure substances that cannot be separated into different substances by ordinary processes Are the building blocks of matter All atoms of an element have the same number of protons 118 elements known today Examples: carbon nitrogen gold Liquid nitrogen.

Name the element found in each! Copper5. Sulfur6. Iodine 1. Carbon2. Sodium3. Aluminum

Symbols of Elements Use 1 or 2 letter abbreviations Capitalize the first letter only Examples: C carbon Cocobalt P Phosphorus Cacalcium Ba BariumMg magnesium

Symbols from Latin Names ElementSymbolLatin name CopperCucuprum GoldAuaurum LeadPbplumbum MercuryHghydrargyrum PotassiumKkalium SilverAgargentum SodiumNanatrium TinSnstannum

Diatomic elements Some elements are composed of two atoms bonded together Whenever you write the symbol for these elements a subscript must be written Oxygen O 2 Nitrogen N 2 Chlorine Cl 2 Iodine I 2

The Periodic Table Represents physical and chemical behavior of elements Arranges elements by increasing atomic number Repeats similar properties in columns known as chemical families or groups

Groups of Elements Vertical columns on the periodic table Similar physical properties Similar chemical properties

Representative Groups Group 1Alkali Metals Group 2 Alkaline Earth Metals Group 17 Halogens Group 18Noble Gases

Periods on the Periodic Table Horizontal rows from Group 1 to Group 18. Numbered 1, 2, 3, ….

Metals- General properties Located on the left hand side Usually solids Lustrous, ductile, malleable Good conductors of heat and electricity Group 1 and 2 metals react with oxygen to form metal oxides which can react with water to from bases (alkaline) Transition metals vary in reactivity, typically hard, high melting points, good conductors of electricity, form ions of variable charge

Non-metals: General properties Located on the right hand side Can be solid (S, P,C) liquid (Br 2 at room temperature) or gaseous (O 2, F 2 ) Dull and brittle solids Poor conductors, good insulators Halogens are extremely reactive Nobel gases extremely unreactive, but Xe, Kr, Rn will react reluctantly with F

Metalloids Do not fit the standard definition of metals or nonmetals Include: Boron, Silicon, Antimony, Germanium, Arsenic, Tellurium Located on the “staircase” of the periodic table

Metals and Nonmetals NONMETALS METALS Transition Metals

Atomic Notation Atomic number: The number of protons in the nucleus of an element (smaller number) Mass number: The average atomic mass of an element (larger number)

Atomic Symbols Show the mass number and atomic number Give the symbol of the element mass number 23 Na sodium-23 atomic number 11

More Atomic Symbols O P Zn __p + __p + __p + __n__ n__n __e - __ e - ___ e -

Energy of Electrons Electrons in atoms are arranged in levels. An electron absorbs energy to “jump” to a higher energy level. When an electron falls to a lower energy level, energy is released. Energy levels are like using a stick shift in a car. The faster you travel the higher gear you use.

The Bohr Model First model made to illustrate electron structure Provides levels where an electron would most likely to be found A Bohr model of Nitrogen.

Electron Levels (Shells) Contain electrons that are similar in energy and distance from nucleus Low energy electrons are closest to the nucleus Higher energy electrons are farther away from the nucleus The first shell (1) is lowest in energy, 2 nd level next and so on 1<2<3<4 Many shells also have sublevels

Number of Electrons per shell Use the formula 2n 2, where n is equal to the energy level n =12(1) 2 = 2 n =22(2) 2 = 8 n =32(3) 2 =18

Periodic Law All the elements in a group have the same electron configuration in their outermost shells Example: Group 2 Be2, 2 Mg 2, 8, 2 Ca 2, 2, 8, 2

Bohr and Lewis Review Valence Electrons: Electrons with the greatest energy Electrons that will react to form compounds Draw the Bohr Diagram for Al Draw the Lewis Diagram for O Draw the Lewis Diagram for the compound formed between Al and O. Name it.

Isotopes Atoms with the same number of protons, but different numbers of neutrons. Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine 35 Cl 37 Cl17 chlorine 35 chlorine 37

Radioisotopes An isotope of an element that is capable of spontaneously emitting radiation in the form of particles and/or gamma rays Occur naturally or can be produced artificially Ex: Tritium 3 1 H Half Life: The time it takes for one 1/2 the nuclei in a radioactive sample to decay Uses: Nuclear power, cancer treatment carbon - 14 dating

Masses of Atoms A measuring unit designed for atoms gives their atomic masses in atomic mass units (u) An atom of 12 C was assigned an exact mass of u The relative masses of all other atoms was determined by comparing each to the mass of 12 C An atom twice as heavy as 12 C has a mass of u. An atom half as heavy is 6.00 u.

Atomic Mass Listed on the periodic table Gives the mass of “average” atom of each element compared to 12 C Average atom based on all the isotopes and their abundance % Atomic mass is not a whole number Na 22.99

Calculating Atomic Mass Percent(%) abundance of isotopes Mass of each isotope of that element Weighted average = mass isotope 1 (%) + mass isotope 2 (%) + …

Atomic Mass of Magnesium Isotopes Mass of Isotope Abundance 24 Mg =24.0 u 78.70% 25 Mg = 25.0 u 10.13% 26 Mg = 26.0 u 11.17% Atomic mass (average mass) Mg = 24.3 u Mg 24.3

Learning Check! Gallium is a metallic element found in small lasers used in compact disc players. In a sample of gallium, there is 60.2% of gallium-69 (68.9 u) atoms and 39.8% of gallium-71 (70.9 u) atoms. What is the atomic mass of gallium ?

Finding An Isotopic Mass A sample of boron consists of 10 B (mass 10.0 u) and 11 B (mass 11.0 u). If the average atomic mass of B is 10.8 u, what is the % abundance of each boron isotope?