Intro to Chemistry

Periodic Table tidbits Period table organization – organized by increasing atomic number Split into metals (left side of stair step line) and nonmetals (right side of stair step line) ONE EXCEPTION Hydrogen! vertical columns (#1-18) Groups horizontal rows (#1-7) Periods

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 1st energy level = holds 2e 2nd energy level = holds 8e 3rd energy level = holds 18e 4th energy level = holds 32e

Subatomic Particles Organized Charge Location Mass Protons Neutrons Electrons

Try it out! Read pp 104-108 then do #3, 4, 5 on page 110

Subatomic Particle Organized Charge Location Mass Protons Positive In nucleus 1 amu Neutrons Neutral Electrons Negative Outside of nucleus/ in energy levels 0 amu Atomic Mass

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

Chemistry tidbits Chemical Symbol- letter representing the atom (sometimes from Latin)

Chemistry tidbits Atomic number = number of protons Don’t kill anyone in my class today! Mass number = # protons + # neutrons Don’t bother to weigh the air inside the box So how can you calculate NEUTRONS??

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

Chemistry tidbits Usually can assume: OK to round atomic mass to nearest whole number # protons = # electrons ONLY true for NEUTRAL ATOMS!

And remember… Don’t mess with the PROTONS!!!

So what CAN we “mess with?” Neutrons… Changes the MASS Get an ISOTOPE Electrons… Changes the CHARGE Get an ION

Atomic Mass Mystery… Look at the atomic mass for Oxygen. What does it say (exactly?) 15.9999 What is the atomic mass? P + N So what the heck!?!?! Average of the actual isotopes on Earth!!!

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… C Nuclear Symbol Notation Includes the symbol, atomic #, and the mass # for that isotope Ex’s 14 6 C

What else CAN we “mess with?” Neutrons… Get an ISOTOPE Electrons… Get an ION

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.

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

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)

Nitrogen 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)

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!!!

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

How do we Draw Atoms Bohr Models Lewis Dot Structures

Look at the many things in your classroom or at home: desks, chairs, windows, shoes, etc. If all of these things are made from atoms and all atoms are made of only a few kinds of particles, what accounts for the variety of things that you see? Atoms of different elements have different atomic numbers. The atomic number tells us the number of protons (+ charge). If the atom is neutral, the number of electrons (-charge) equals the number of protons. The mass number is the number of protons + the number of neutrons (0 charge). In the following, C-14, the 14 is the mass number. The atomic number for C can be found on the periodic table. C’s atomic number is 6, so it has 6 protons and 6 electrons. To find the neutrons, take the mass number minus the protons (14-6 = 8 neutrons). In the Bohr Model, the protons and the neutrons are placed in the atomic nucleus while the electrons orbit around the nucleus in stationary levels. Each level can hold only a certain maximum number. The 1st up to 2 electrons, the 2nd up to 8 electrons, the 3rd up to 18 electrons, and the 4th up to 32 electrons.  

Complete the table below using the information given for each atom 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 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 3 4 7 B 11 12 23 C 19 20 39 D 17 18 35

Let’s Draw some 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 Also the GROUP NUMBER!!!

Valence Electrons are what react!

Lewis Dot Structures Lewis dot diagrams- display the number of valence electrons (outermost electrons) around the element symbol Used to show how atoms of different elements bond and form compounds Hint- use group number to find valence electrons

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

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

EXCEPTIONS!!! Helium- What is its group number? Why doesn’t it make sense to draw that many dots? Because it is easier for it to fill that first shell which only needs two electrons

Electron configurations (Bohr Models)

Lewis Dot Structures