Atoms and The Periodic Table Learning Targets: Describe atoms Use the Periodic Table

Atoms What are atoms? Atoms are the basic building blocks of matter that make up everyday objects. A desk, the air, even you are made up of atoms! There are 90 naturally occurring kinds of atoms. Scientists in labs have been able to make about 25 more.

Structure of Atoms All atoms are made of a nucleus, or center surrounded by orbits of electrons

The nucleus is made up of 2 kinds of particles: Protons-which have a positive charge. The number of protons determines what element you have. Neutrons-- which have no charge. The number of neutrons usually matches the number of protons, but isotopes of an element may have different numbers of neutrons.

Around the nucleus of an atom, are orbits of electrons. Electrons are very small, negatively charged particles. Their negative charge attracts them to the positively charged protons in the neucleus.

With your partner, describe these 3 particles that make up all atoms: Electron Proton Neutron

Electron orbits exist in several shells or energy levels. First energy level Second energy level

Scientists often illustrate the electron arrangement with a drawing called a Bohr diagram. This shows the placement of the electrons into their energy levels. Atoms like to have their outside energy level full. If it is not, they are more likely to react with other atoms.

Elements react when they give, take or share electrons from other elements. Water is formed when 2 hydrogen atoms share electons with 1 atom of oxygen

Discuss with your partner: How are electrons arranged? What does a Bohr diagram show you? What is likely to happen if elements DON’T have their outer electron level full? What happens when one atom reacts with another atom?

Clues to the answers to these questions can be found What would you expect different elements to be like? Which elements are most likely to react? What will they be likely to react with? Clues to the answers to these questions can be found in a tool called THE PERIODIC TABLE.

The Periodic Table Organization of the Elements

Search for Order 1750 only 17 elements known 1789 Antoine Lavoisier grouped known elements (4 groups) Metals Non-metals Gases Earths Next 80 yrs scientists looked for better way to classify known elements

Mendeleev’s Periodic Table 1869….Dmitri Mendeleev (Russian teacher and chemist) organized known elements while playing solitaire Made deck of cards with elements Listed name, mass and properties Paid attention to how elements reacted in chemical reactions

Mendeleev’s Periodic Table Strategy for organization: What did he look at? chemical properties physical properties atomic mass density color melting point Valence electrons (sec 5.3)

Mendeleev’s Proposal Elements arranged in rows based on increasing mass. Elements with similar properties are in same column. Chart was a Periodic Table - arrangement of elements in columns based on a set of properties that repeat.

Mendeleev’s Prediction Table incomplete– elements not yet discovered Left spaces in table for undiscovered elements Good models allow for predictions to be made based on model Used properties of nearby elements to predict properties of unknown elements

He called this element eka-Aluminum. Later it was renamed Gallium after its discovery in 1875

Evidence Supporting Mendeleev’s Table Close match between Mendeleev’s predictions and the actual properties of new elements showed how useful table was. Ex. Discovery of: Aluminum, Gallium, Scandium, and Germanium http://www.iteachbio.com/Chemistry/Chemistry/The%20Periodic%20Table.mov

The Modern Periodic Table YOU NEED 3 DIFFERENT COLORED PENCILS Section 5.2 The Modern Periodic Table The Elements by Tom Lehrer

The Modern Periodic Table “Periodic” - Repeating patterns Listed in order of increasing number of protons (atomic #) Properties of elements repeat Periodic Law- when elements arranged by increasing number of protons, properties repeat in pattern

Columns in the Periodic Table -vertical (up & down) -called groups or families -#ed 1-18 or 1A through 8A -elements in same family have similar properties

Rows in the Periodic Table -horizontal (left – right) -called a period -properties change greatly across period -first element in period is very active metal -last element in most periods is noble gas -7 periods (number them on your periodic table)

Discuss with your partner: Why is a chemists chart called a PERIODIC table—what does periodic mean?

6 C Carbon 12.01 For example: Carbon has atomic # 6 Element Key Important information about an element is given in each square of the periodic table: its atomic number chemical symbol element name average atomic mass 6 C Carbon 12.01 For example: Carbon has atomic # 6 (or has 6 protons), an average atomic mass of 12.01 and a symbol of C

What are 4 important pieces of information each square of the Periodic Table gives you about its element?

Metals Most solids (Hg is liquid) Luster – shiny. Ductile – drawn into thin wires. Malleable – hammered into sheets. Conductors of heat and electricity. Include transition metals – “bridge” between elements on left & right of table

Non-Metals Properties are generally opposite of metals Poor conductors of heat and electricity Low boiling points Many are gases at room temperature Solid, non-metals are brittle (break easily) Chemical properties vary

Metalloids stair-step pattern Have properties similar to metals and non-metals Ability to conduct heat and electricity varies with temp Better than non-metals but not metals

Representative Groups Section 5.3 Representative Groups Hip Hop Classroom The Elements

What are Valence electrons? outermost e-’s Responsible for chem props Elements in same group… same # of VE ALL atoms want full outer energy level (usually 8 VE) To get full outer energy level, some elements: lose e- (metals) gain e- (non-metals) share electrons (some non-metals & metalloids)

What are valence electrons? Why are they important?

Introducing the ten major groups (families) on the modern Periodic Table:

Hydrogen is not a member of this group. Alkali Metals potassium - 1 valence electron (VE) - soft, silver-white, shiny metals never found pure most reactive metals Reactivity increases down group Hydrogen is not a member of this group. It is not a metal. reactivity increases

Label the Alkali Metals to your PT

Alkaline Earth Metals - 2 VE - not as reactive as alkali metals magnesium - 2 VE - not as reactive as alkali metals often mixed with Al forms strong/light weight alloys

Alkaline Earth Metals Magnesium Calcium Used to make steel (light metal w/o losing strength) photosynthesis (chlorophyll) Calcium bones & teeth Chalk, limestone, pearls, plaster

Label the Alkaline Earth Metals to your PT

Boron Family -3 VE Boron Hard/brittle never found pure in nature in borax...used to make detergents & cosmetics

Boron Family 13 Al Aluminum 26.98 Aluminum most abundant metal in earth’s crust important metal for industry light, strong, slow to corrode 13 Al Aluminum 26.98

Label the Boron Family on your PT

Carbon Family 4 VE Can gain 4 e-, lose 4 e-, or share e- silicon 4 VE Can gain 4 e-, lose 4 e-, or share e- Most compounds in body contain C Si 2nd most abundant element in Earth’s crust Si used to tip saw blades

Label the Carbon Family on your PT

Nitrogen Family 5 VE Tend to gain 3 e- N and P used in fertilizers Arsenic 5 VE Tend to gain 3 e- N and P used in fertilizers P on tips of matches

Label the Nitrogen Family on your PT

Oxygen Family 6 VE Tend to gain 2 e- O very abundant element sulfur Oxygen Family 6 VE Tend to gain 2 e- O very abundant element S used in fertilizers O needed for digestion

Label the Oxygen Family on your PT

Halogen Family (“salt-former”) -7 VE -most active nonmetals -never found pure in nature -react with alkali metals easily (forms salts) -F most active halogen

F compounds in toothpaste Cl kills bacteria Halogens cont… bromine F compounds in toothpaste Cl kills bacteria I keeps thyroid gland working properly

Label the Halogen Group on your Periodic Table

The Noble Gases (Inert Gases) Neon - non-reactive outermost e- shell is full (8 VE) In “neon” lights -in earth’s atmosphere (less than 1%)

Label the Noble Gases on your Periodic Table

Discuss: What are chemical “families”? How are they different from periods?

Transition Metals ductile, malleable, conductors mercury Almost all solids at room temp (Hg exception) ductile, malleable, conductors VE varies Less Reactive than Groups 1 & 2 Fe, Co, and Ni produce magnetic field

Label the Transition Metals on your periodic table

Rare Earth Elements Lanthanide series (period 6) uranium Lanthanide series (period 6) Actinide Series (period 7) Some radioactive Separated from table to make easy to read/print silver, silvery-white, or gray metals. Conduct electricity

Label the Lanthanide Series on your PT

Label the Actinide Series on your PT

You may watch more videos about the elements at: http://www.periodicvideos.com/ or sing along at: http://www.youtube.com/watch?v=zGM-wSKFBpo&feature=related elemental funkiness - Mark Rosengarten hip hop classroom

Did you reach our learning targets? Describe atoms Use the Periodic Table Use the table to describe oxygen.