Intro to Chemistry

Atomic Structure Nucleus- center of an atom -contains protons (which are positive) -contains neutrons (which are neutral) Ex- Sodium:

Atomic Structure Outside the Nucleus: Electrons (which are negative) surround the nucleus in energy levels Outermost electrons are called valence electrons

An atom is defined by the number of PROTONS IT HAS!!!

Atomic Mass Unit (AMU) The unit of measurement for an atom is an AMU. It stands for atomic mass unit. One AMU is equal to the mass of one proton.

Atomic Mass Unit (AMU) There are 6 X or 600,000,000,000,000,0 00,000,000 amus in one gram. (Remember that electrons are 2000 times smaller than one amu).

Subatomic Particles Organized ChargeLocationMass Protons Neutrons Electrons

Subatomic Particle Organized ChargeLocationMass ProtonsPositiveIn nucleus1 amu NeutronsNeutralIn nucleus1 amu ElectronsNegative Outside of nucleus/ in energy levels 0 amu Atomic Mass

Try it out! Read pp then do #3, 4, 5 on page 110

The Periodic Table can tell us a lot about the elements.

What’s in a square? Chemical Symbol- letter representing the atom (sometimes from Latin) ALWAYS write the first letter capital and second letter lower case  Ex- Cu, Fe, Rb

Symbols All elements have their own unique symbol. It can consist of a single capital letter, or a capital letter and one or two lower case letters. C Carbon Cu Copper

Atomic number = number of protons  Don’t kill anyone in my class today! Mass number = # protons + # neutrons  Don’t use the one on the PT unless you have to! That is an average! Use the Mass # given for that element!

Calculating Neutrons is a simple algebraic problem… Atomic Mass = protons + neutrons Atomic Number = protons Write the equation…  Mass # = protons + neutrons  #Neutrons = (mass number – atomic number)

What about Electrons? In a NEUTRAL atom, every + (proton) is balanced by a –(electron). Therefore, in a neutral atom, protons=electrons and you can use the following mneumonic: A = P =E (atomic #) = (protons) = (electrons)

Complete the table below using the information given for each atom. Atom A has 3 protons and 4 neutrons. Atom B has 11 protons and 12 neutrons. Atom C has an atomic number of 19 and a mass number of 39. Atom D has an atomic number of 17 and a mass number of 35. Atom# of protons # of neutrons Atomic #Mass ## of electrons A B C D

Complete the table below using the information given for each atom. Atom A has 3 protons and 4 neutrons. Atom B has 11 protons and 12 neutrons. Atom C has an atomic number of 19 and a mass number of 39. Atom D has an atomic number of 17 and a mass number of 35. Atom# of protons# of neutrons Atomic #Mass ## of electrons A B C D

Try it out! (Blue Worksheet) Check answers at front…move onto yellow sheet if doing well NEED TO KNOW…  Nuclear Symbol notation: Mass # Atomic #  Mass hyphen notation: Symbol- Mass ex: N-14 Symbol

Atomic Mass Mystery… Look at the atomic mass for Oxygen. What does it say (exactly?)  What is the atomic mass?  P + N So what the heck!?!?!  Average of the actual isotopes on Earth!!!

How can we change the mass of an element? We can’t mess with protons, but what CAN we “mess with?”  Neutrons… What would that change about the atom? Changes the MASS Get an ISOTOPE

Isotopes Isotopes are different atoms of the same element that contain the same number of protons but different number of neutrons. Examples Cl-35 vs. Cl-37 17P 17P 18N 20N

How to write isotopes… Mass/Hyphen Notation:  Especially important for a form of the isotope that is NOT the “usual”  Write the symbol, a dash, and the mass # for that isotope  Ex’s C-14 C-12

How to write isotopes… Nuclear Symbol Notation  Includes the symbol, atomic #, and the mass # for that isotope  Ex’s 14 6 C Mass # Atomic # (=p)

How do we Draw Atoms? Bohr Models Lewis Dot Diagrams

How to draw a Bohr Model 1. Draw a nucleus & put protons and neutrons inside.  (may use a square shape so you don’t draw any electrons on it) 2. Remember the p=e in a neutral atom, so begin putting electrons on the energy levels until you use them all up.  Fill energy levels in order (can’t put any in 2 nd shell until you’ve filled the first)

Drawing Bohr models, cont… Helpful hints: 1. Draw electrons at each of the four “corners”, then double up 2. Write the number of electrons you drew (in parentheses) on each energy level to help you keep track.

Electron configurations (Bohr Models)

But…that can be a pain… Most of the time we only really care about the valence electrons Valence Electrons- electrons in the outermost shell  Use the GROUP NUMBER!!!

Valence Electrons- Find the number of valence electrons by counting over the rows (skipping transition metals)

Notice- rows 13, 14, 15, 16, 17, 18 have 3, 4, 5, 6, 7, and 8 valence electrons respectively.

Valence Electrons are what react!

How to draw a Lewis Dot Structure 1. Use the group # (top of the row on the PT) to determine # of valence electrons 2. Write the symbol. 3. Draw dots around the symbol equal to the # of valence electrons (if group 2- draw two dots) 1. Place dots one at a time around the top, right, bottom and left side of the atom before you double any up.

How to draw a Lewis Dot Structure 1. Find the group # (top of the row on the PT) Let’s do Phosphorus 2. Write the symbol. P 3. Draw dots around the symbol equal to the group number (if group 2- draw two dots) 1. Place dots one at a time around the top, right, bottom and left side of the atom before you double any up.

Octet Rule- Most atoms want to have 8 electrons in their outer shell.

Octet rule exceptions… (octet rule=Most atoms want to have 8 electrons in their outer shell) Helium-  What is its group number?  Why doesn’t it make sense to draw that many dots?  Because it only has 2 electrons TOTAL!

Elements with a full outer shell naturally

Lewis Dot Structures

Families on the Periodic Table

Elements Science has come a long way since Aristotle’s theory of Air, Water, Fire, and Earth. Scientists have identified 90 naturally occurring elements, and created about 28 others.

Elements The elements, alone or in combinations, make up our bodies, our world, our sun, and in fact, the entire universe.

Mendeleev In 1869, Dmitri Ivanovitch Mendeléev created the first accepted version of the periodic table. He grouped elements according to their atomic mass, and as he did, he found that the families had similar chemical properties. Blank spaces were left open to add the new elements he predicted would occur.

Periodic Table Organizes elements in a particular way All the elements in this column (“family”) have similar properties. That’s why they are grouped together.

EX- Valence electrons can be determined from the group number!

What does it mean to be reactive? We will be describing elements according to their reactivity. “Reactive Elements” do not have a full outer shell of electrons. Therefore, they will “react” with other elements to get a full outer shell.

First let’s draw our staircase in black…

Make a chart Metals Nonmetals

Properties of Metals Physical Properties of Metals…  Solid at room temperature  good conductors of heat and electricity.  shiny.  ductile (can be stretched into thin wires).  malleable (can be pounded into thin sheets). A chemical property of many metal is its reaction with water which results in corrosion. (rust)

Properties of Non-Metals Physical properties of Non-metals …  poor conductors of heat and electricity.  not ductile or malleable Solid non-metals are brittle and break easily.  dull.  Many non-metals are gases. Sulfur

Properties of Metalloids/Semiconductors Metalloids (metal-like) have properties of both metals and non-metals.  They are solids that can be shiny or dull.  They conduct heat and electricity better than non- metals but not as well as metals.  They are ductile and malleable. Silicon

Families Periods Columns of elements are called groups or families. Elements in each family have similar but not identical properties.  For example, lithium (Li), sodium (Na), potassium (K), and other members of family IA are all soft, white, shiny metals. All elements in a family have the same number of valence electrons. Each horizontal row of elements is called a period. The elements in a period are not alike in properties.  In fact, the properties change greatly across even given row.  The first element in a period is always an extremely active solid. The last element in a period, is always an inactive gas.

Hydrogen Hydrogen is in a family of its own. It’s a nonmetal on the metal’s side  It’s a gas at room temperature.

Alkali Metals Group one the first column of the periodic table. 1 valence electron. All metal properties (They are shiny, etc) Soft metals: easily cut with a knife.

Alkali Metals They are the most reactive metals. They react violently with water. Vk Vk Alkali metals are never found as free elements in nature. They are always bonded with another element.

Use Purple

Alkaline Earth Metals Group 2 Second column of metals (Properties of metals) Also very reactive (but not as reactive as Alkali metals) They have two valence electrons.

Transition Metals Big group in the middle.  (group varies) Properties of metals. (They are good conductors of heat and electricity, etc.) Everything else varies (valence electrons, reactivity, etc)

Use orange

Halogen Family Group 17 Second column from the right. Halogens have 7 valence electrons, which explains why they are the most reactive non-metals. They are never found free in nature. They react with alkali metals to form salts.

Use Red

Noble Gases Group 18 8 valence electrons colorless gases extremely un-reactive.  Becauses their outermost energy level is full. called inert.

Rare Earth Elements The thirty rare earth elements are composed of the lanthanide and actinide series. One element of the lanthanide series and most of the elements in the actinide series are called trans-uranium, which means synthetic or man-made.

The next 4 families are named by the element at the top of the row Boron Family- group 13  3 valence electrons Carbon Family- group 14  4 valence electrons Nitrogen Family- group 15  5 valence electrons Oxygen Family- group 16  6 valence electrons

Predicting Ion Formation

Let’s look at our families- What ion will each form? It all starts with the noble gases… Everyone wants to be NOBLE

These are the “magic numbers” Each of these atomic numbers will make a “full outer shell” Other families will lose or gain electrons to get the these “numbers”

Alkali Metals All (except hydrogen- of course) will lose one electron to form a __________ charge.  (+1)

Alkaline Earth Metals All will lose two electrons to form a __________ charge.  (+2) Ex- A neutral Mg atom has 12 protons and 12 electrons (+12) + (-12) = 0 A Mg ion has 12 protons and only 10 electrons (+12) + (-10) = +2

Boron Family All will lose three electron to form a ____ charge.  (+3)

Carbon Family is special All have four valence electrons, so it can lose four OR gain four to fulfill its octet! So it can form a _____ or a ______ion! -(+4) or (-4)

Nitrogen Family All have five valence electrons, so it can gain three to fulfill its octet! So it can form a ________ion! - (-3)

Oxygen Family All will gain two electrons to form a __________ charge.  (-2) Ex- A neutral Oxygen atom has 8 protons and 8 electrons (+8) + (-8) = 0 An Oxygen ion has 8 protons and 10 electrons (+8) + (-10) = (-2)

HALOGENS All will gain one electrons to form a __________ charge.  (-1)

How about those noble gases? They will NOT FORM IONS!!!

What subatomic particles CAN we “mess with?” Already know…Neutrons…  Get an ISOTOPE, changes the mass But what if I mess with Electrons…  What would that change about the atom?  Changes the CHARGE  Get an ION

Intro to Ions

How are these ions made? Can you mess with protons? Would messing with neutrons do anything to the charge? What must you mess with??? What charge does an electron have? So what would happen to the atom if they LOSE one? Would they get more positive or more negative overall???

IONS If you mess with the electrons you change the overall charge of the atom…an atom that is no longer neutral is called an ION. ANION- has a negative charge  Means you added an electron! CATION- has a positive charge  Means you lost an electron