Unit 2/B: Chemical Interactions Chapter 5: Atomic Structure and the Periodic Table Chapter 6: Chemical Bonds and Compounds Chapter 7: Chemical Reactions Chapter 8: Solutions Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Chapter 5: Atomic Structure and the Periodic Table A substance’s atomic structure determines its physical and chemical properties 5.1 Atoms are the smallest form of elements 5.2 Elements make up the periodic table 5.3 The periodic table is a map of the elements Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

5.3 The periodic table is a map of the elements Before, you learned: The periodic table is organized into groups of elements with similar characteristics The periodic table organizes elements according to their properties Now, you will learn: How elements are classified as metals, nonmetals, and metalloids About different groups of elements About radioactive elements Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Warm-up questions Refer to the periodic table – how are each pair of elements related? Calcium and barium In the same group Lithium and carbon In the same period Uranium and curium In the same period and in the actinide series Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Numbers and Mass Numbers All atoms are composed of the same particles… Different numbers of protons in the nucleus Atomic number = # protons in the nucleus Atomic mass number = # protons + # neutrons Same elements have same # protons but not always the same # neutrons, so may have different atomic masses Ex: Chlorine atoms have 17 protons, some have 18 neutrons, some have 20 neutrons = Chlorine isotopes Isotopes: atoms of the same element that have a different number of neutrons Chlorine-35, Chlorine-37 # protons? # neutrons? Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

How to Read the Periodic Table? The number at the top is the atomic number = # protons in the nucleus Chemical symbol - one or two letters; temporary symbols for not-yet named elements have three-letter symbols Name of element number at bottom is the “average atomic mass” of all the isotopes of the elements Color of symbol is the state of matter at room temperature Color of background color of box indicates whether metal, nonmetal, or metalloid (5.3) Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Groups and Periods Elements in a vertical column show similarities in their chemical and physical properties Known as a group Labeled by a number at the top of the column Sometimes a group is called a family of elements because they seem to be related Ex: Group 17 – “Halogen” group Tend to combine easily with other elements and compounds, especially elements in Gropus 1 and 2 Different physical properties At room temperatures: Flourine and chlorine are gases, bromine is a liquid, iodine and astatine are solids Ex: Group 1 – Some metals – lithium, sodium, potassium, for example – react violently with water Horizontal row in the periodic table = period Properties of elements change in a predictable way from one end of a period to the other Ex: Period 3 = elements on far left are metals, far right are nonmetals Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

The periodic table has distinct regions Like a map! Different areas indicate the properties of the elements Three main regions: Metals on the left (yellow) Nonmetals on the right (except hydrogen) (green) Metalloids in between (purple) Reactive – how likely an element is to undergo a chemical change – combining with other materials Atoms in Groups 1 and 17 are the most reactive Group 18 is the least reactive Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

To which group do most elements belong? Most elements are metals – look! (yellow) Metals elements that conduct electricity and heat well have a shiny appearance Can be shaped easily by pounding, bending, wire Most are solids at room temperature (except _______) Mercury Na - sodium Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Steel – mostly iron (some carbon) Brass – zinc &copper Bronze - copper & tin Steel – mostly iron (some carbon) Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Reactive Metals (Group 1) Group 1 – the “alkali metals” Sodium, potassium – often stored in oil to keep from air as they react rapidly with oxygen and water vapor Ions: ____ and ____ are important in living cells (hint: which side of the periodic table loses/gains electrons) Group 2 – “alkaline earth metals” Less reactive than the alkali metals, more reactive than other metals Calcium ions – essential to bones, teeth Magnesium – light, inexpensive metal – combined with other metals – airplane frames Na+ K+ left side loses electrons, forming a positive ion. Group 1 loses 1 electron…hence Na+ and K+ Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Transition Metals Groups 3-12 Copper, gold, silver, iron Generally less reactive than most other metals Jewelry and coins: Gold and silver – easily shaped and not reactive – used for thousands of years Artifacts found in museums: unchanged -they last Coins: Dimes and quarters made of nickel – pennies made of zinc and copper Industry: Iron – main part of steel Electric wires & Pipes – copper Modern Technology – tungsten – incandescent light bulbs Alloys – two or more metals combined Can be stronger , less likely to corrode, or easier to shape than pure metals Steel: iron + [nickel, chromium, manganese] (stronger than iron alone) Brass: copper + zinc (stronger than either alone) Jewelry: silver + copper (stronger than silver alone) Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Rare Earth Elements (metals) Top row of the two rows of metals shown outside the main body of the periodic table “Lanthanides” (they follow lanthanum on the table) Once believed only to be found in tiny amounts in Earth’s crust Not as rare as originally thought – just hard to isolate in pure form Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Nonmetals and metalloids Have a wide range of properties Nonmetals: Many are gases at room temperature One is a liquid (Bromine) Solids often have a dull surface and cannot be shaped by hammering or wires Poor conductors of heat and electric current Ex: air – nitrogen and oxygen – both gases, different properties Nitrogen is fairly unreactive Oxygen readily reacts – rusting, burning Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Halogens (nonmetals) Group 17 Halogens means “forming salts” Very reactive Often used to kill harmful microorganisms Ex: chlorine, iodine Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Noble Gases (nonmetals) Group 18 Noble = inert gases – almost never react with other elements Ex: colorful lights – pass an electric current through tubes of neon, krypton, xenon, argon gases glow Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Metalloids Properties of both metals and nonmetals Most common is silicon (Si) The second most common atoms in Earth’s crust Uses: Semiconductors found in electronic devices Conduct electricity under some conditions and not under others Used in computer chips (silicon, gallium, germanium) Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Some atoms can change their identity How is identity determined? # protons in _________ The nucleus Chemical changes do not affect the nucleus, so chemical changes don’t change one type of atom into another BUT…conditions may cause the number of protons to change…does this change the type of atom? Yes! Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Some atoms can change their identity Stability of a nucleus depends on the right balance of protons and neutrons Too few or too many neutrons, the nucleus may become unstable Particles are then produced from the nucleus of the atom to restore balance Results in a release of energy May change the number of protons  different element! Radioactivity – the process by which atoms produce energy and particles Isotope is radioactive if the nucleus has too many or too few neutrons Radioactive isotopes are more rare for lighter elements more common for heavier Measured using a Geiger counter – detects particles from the break up of the atomic nucleus - clicks Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Radioactivity and Medicine Used to diagnose and treat patients Destroy harmful tumors Monitor activity of certain organs in body – inject a radioactive isotope and determine where and how the body is using a substance Large does are harmful Damage or kill cells Energy from its particles can burn the skin Prolonged exposure linked to cancer Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Radioactive Decay Energy and particles are produced from the nucleus of radioactive atoms Radioactive decay – when the number of protons, and the identity of the atom, changes Occurs at a steady rate characteristic of the particular isotope Half-life – the amount of time it takes for one-half of the atoms in a particular sample to decay Ex: 1000 atoms of radioactive isotope with half-life of 1 year…how many atoms would have changed one year later? After another year? Not affected by temperature or pressure Can range from fractions of a second to billions of years Simulation: http://www.colorado.edu/physics/2000/isotopes/radioactive_decay3.html Animation: http://holbert.faculty.asu.edu/eee460/eee460.html 1000, 500, 250 Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties