Properties of Atoms and the Periodic Table Chapter 17 Pages 504-533

Section 1: Structure of the Atom

What is an atom??? First, let’s review what an element is: An element is matter that is composed ONLY of one type of atom. An atom is the smallest piece of matter that still retains the properties of the element. Example: The element oxygen is composed of only oxygen atoms.

Composition of Atoms Atoms are composed of 3 general particles: Charge Location Proton Positive (+) Nucleus Neutron No charge (neutral) Electron Negative (-) Outside the Nucleus

How are atoms of the various elements different??? Atoms of different elements contain DIFFERENT NUMBERS OF PROTONS!!!

Quarks Quarks are very small particles that make up both protons and neutrons! At this time, scientists do not think that electrons can be broken down into smaller pieces.

Finding Quarks To study quarks, charged particles are accelerated (almost to the speed of light) and forced to collide with a proton. The collision causes the proton to break apart. The Large Hadron Collider, located in Switzerland and France, consists of a circular tunnel with a circumference of 17 miles! http://www.wimp.com/largehadron/

Finding Quarks

The Changing Atomic Model 400 BC: Democritus proposed the idea that atoms make up all substances. Aristotle said matter was uniform throughout and was not composed of smaller particles. 1800’s: John Dalton proved atoms exist.

The Electron Cloud Model An electron cloud is the area around the nucleus of an atom where the electrons are most likely to be found. The electron cloud is 100,000 times larger than the diameter of the nucleus. Electrons are MUCH smaller than protons.

Atomic Model Example Example: We want to build a model of a hydrogen atom. We will represent the nucleus with a marble that has a radius of 2.4 cm. Any guesses as to how big we need to make the entire atom??? 1.2 kilometers!!!!!!!

Section 2: Masses of Atoms

Atomic Mass Protons and Neutrons have about the same mass (1.67 x 10-24g)……VERY small Both protons and neutrons have 1,836 times more mass than an electron. Atomic Mass Unit (AMU) is the measurement used for the mass of a proton or neutron.

What element is it? You need to know how many protons it has! The number of protons in an atom is equal to the atomic number.

Mass Number The mass number of an atom is the sum of the number of protons AND the number of neutrons in the nucleus.

So how do you find the number of Neutrons??? mass # - atomic #

Lets Do an Example Element: Strontium, (#38) Atomic Number: 38 Mass Number: 88 Number Protons: 38 Number Neutrons: 50 Number Electrons: 38

Carbon Dating…What is it??? Carbon dating uses isotopes of carbon that are radioactive and have a half-life to date once living organisms.

Wrong King of Carbon Dating This is NOT carbon dating.

Isotopes Isotopes are atoms of the same element with different numbers of NEUTRONS!!!!

Identifying Isotopes To identify each isotope, write the mass number of the isotope behind the element name: Boron-10 Boron-11 The average atomic mass is the weighted –average mass of the mixtures of it’s isotopes.

Isotope Example Chromium-58 Chromium-63 # Protons: _____ # Neutrons: _____ # Electrons: _____ Chromium-63

Section 3: The Periodic Table

Organizing the Elements Late 1800’s Dmitri Mendeleev, Russian chemist Ordered elements by increasing atomic masses. Left blank spaces in the table to keep the elements lined up. He predicted the properties of elements not yet discovered! (and was accurate!)

Organizing the Periodic Table The vertical columns are labeled 1-18 and are called groups. The horizontal columns are labeled1-7 and are called periods Elements in each group have similar properties

Electron Cloud Structure Electrons are located outside of the nucleus of an atom…but do we know exactly where? Electrons have different amounts of energy, and exist in different energy levels within the atom.

Continued…electron cloud structure The closest electrons to the nucleus have the lowest amounts of energy, where the farthest electrons away from the nucleus have the most energy. Elements in the same group have the same number of electrons in their outer energy level.

Implications of Electron Cloud Structure The number of electrons in the outer energy level determines the chemical properties of that element. Electrons in the outer energy level also called Valence Electrons.

Electron Dot Diagrams Electron dot diagrams use the symbol of the element and dots to represent the electrons in the outer energy level. Also can be called Lewis Structures.

Bohr Structures Bohr Model- includes all electrons.

Elements in the Universe Z Element Parts per million 1 Hydrogen 739,000 2 Helium 240,000 8 Oxygen 10,400 6 Carbon 4,600 10 Neon 1,340 26 Iron 1,090 7 Nitrogen 960 14 Silicon 650 12 Magnesium 580 16 Sulfur 440

Elements and Their Properties Chapter 19 Pg. 568-599

Section 1: Metals

Properties of Metals 1. Good conductors of heat and electricity 2. All but mercury are solid at room temperature.

More Properties of Metals 3. Metals reflect light. This property is called luster

More Properties of Metals 4. Metals are malleable- they can be hammered or rolled into sheets. 5. Metals are ductile- they can be drawn into wires.

Ionic Bonding in Metals Metals usually have 1-3 electrons in their outer energy levels. Metals can “give” one or more of their outer electrons to another atom, thus bonding them together by sharing electron(s).

Metallic Bonding Metallic bonding-electrons in outer energy level are shared between all the atoms.

Alkali Metals Group 1 Softer than most metals Most reactive of all the metals especially with air and water. Do not exist in the earth in their elemental form, so they are stored in substances that are not reactive, like oil. Group 1 Alkali metals have 1 electron in their outer shell, And combine easily with group 17 elements.

Alkaline Earth Metals Group 2 of the Periodic Table Each atom of this group has 2 valence electrons.

Alkaline Earth Metals- Uses Fireworks! Magnesium makes a white explosion, and strontium produce red. Magnesium used in making cars, planes, and spacecraft. Our bones need calcium to keep them strong.

Transition Elements Found in groups 3-12 in the Periodic Table Often form colored compounds. Example gems (chromium), some paints made from compounds of cobalt and/or cadmium.

Iron, Cobalt and Nickel All three elements are used to make steel, with iron making up most of steel. Nickel is added to give extra strength and to give a shiny, protective coating.

Copper, Silver and Gold Group 11 Called “coinage metals” because they were once used to make coins. (now most coins are made of nickel and copper!) Copper used in electrical wiring Compounds containing silver help with making photographs appear on paper. Silver and gold used in jewelry.

Zinc, Cadmium, and Mercury Group 12 Cadmium is used in rechargeable batteries Mercury- the only metal that is a liquid at room temperature. Used in thermometers, thermostats, and batteries. Mercury is VERY poisonous!!!

The Inner Transition Metals Lanthanides and Actinides. Lanthanides #’s 58-71, named because they follow the element Lanthanum (#57) Actinides #’s 90-103, named because they follow the element Actinium (#89) All actinides are radioactive and unstable! Ex: Uranium used for nuclear energy.

Metals in the Earth’s Crust Metals are mined and then separated from other rock. Most platinum is located in South Africa.

Ores: Minerals and Mixtures Ore: made of a metal compound, or mineral, within a mixture of clay and/or rock. Process: Separate rock from mineral. Roasting- mineral converted to another physical form-uses heat Metal refined into pure form.

Section 2: Nonmetals

Properties of Nonmetals Nonmetals are usually gases or brittle solids at room temperature. Nonmetals are not malleable or ductile. They do not conduct heat or electricity, they are not shiny. Nonmetals are found to the right side of the periodic table (plus Hydrogen)

Elements in the Human Body

Bonding in Nonmetals Nonmetals can form ionic and covalent compounds. Examples: textbook pg. 579 Pb + S = PbS

Hydrogen Hydrogen in it’s gas form is a diatomic molecule: it consists of two atoms of the same element held together with a covalent bond. Example: H2 Hydrogen is VERY reactive. It has one electron and can combine with other elements to share the electron.

Halogens Group 17, includes F, Cl, Br, I, and At Seven valence electrons in outer energy level.

Uses of Halogens Chlorine is used to disinfect pool water. Iodine is a solid at room temperature and when heated changes directly to a gas: the process of sublimation!

The Noble Gases Stable because they have full outer energy levels.

Section 3: Mixed Groups

Properties of Metalliods Metalloids share properties of both metals and nonmetals. Metalliods also called SEMICONDUCTORS because they can conduct electricity better than nonmetals, but not as well as metals.

The Boron Group Group 13 Boron is a metalliod. Household items that contain compounds of boron are borax (used in laundry detergent) and boric acid (insecticide). Aluminum is the most abundant metal in earth’s crust, and is used in soft-drink cans, foil wrap, and to construct airplanes.

The Carbon Group Each element in group 14 has 4 valence electrons. Carbon is a nonmetal and is found in coal, oil, natural gas, and foods. Plants use carbon dioxide and sunlight to make glucose.

Continued…The Carbon Group Allotropes are different forms of the same element. Example: Carbon: Diamond and Graphite

Semiconductors Silicon is the main component in semiconductors, Germanium is also used Semiconductors: (elements that conduct an electric current under certain conditions). Tin used to coat other metals to prevent corrosion. Lead was once used in paints, but is no longer because it is toxic!

The Nitrogen Group Group 15- Each element has 5 valence electrons. Nitrogen makes up 80% of the air we breathe, and is the 4th most abundant element in our bodies. Bismuth and Antimony are metals that are used in fire-sprinkler heads because they help to lower the melting points.

The Oxygen Group Group 16, Oxygen used by all living things to breathe. Sulfur compounds used for pigments in paints. Selenium needed in the body in VERY small amounts, too much is toxic. Also used to make photocopies.

Synthetic Elements Scientists create elements by smashing existing elements in a particle accelerator. Example: Smashing uranium with neutrons can make neptunium. Neptunium atoms only last for about 2 days, and when they disintegrate, they form plutonium.

Transuranium Elements Elements with more than 92 protons. They are synthetic, unstable, and many of them disintegrate quickly.