The Atom & the Periodic Table

Jen Rosenthal

Review of the AtomFill in the following table based on what you learned from last class about the

atom.

Subatomic Particle

Location within the atom

Charge Mass

neutron In the nucleus 0 or neutral 1 amu

proton In the nucleus +1 1 amu

electron Outside of the nucleus

-1 0 amu

History of the Periodic TableDmitri Mendeleev

• Searched for way to organize elements• Put them in order of increasing masses

How do you read the periodic table?

Parts of the Periodic Table

What you need to know

http://www.classzone.com/books/earth_science/terc/content/investigations/es0501/es0501page06.cfm

Key Terms to UnderstandTerm Definition Example

Atomic Number Equal to the # of protons in the nucleus and the # electrons in the electron cloud

Carbon (6) has 6 protons and 6 electrons

Atomic Mass Average mass of all of the element’s isotopes

Carbon (12.01) amu which is unified atomic mass units

Mass Number/Atomic weight

The sum of the protons + the neutrons (# of protons + # of neutrons)

Carbon (12.01), where 12.01 amu represents the sum of protons (6) + neutrons (6)

Isotope Two nuclides (a particular kind of nucleus) that have the same atomic number but a different mass number

24Mg (79% of all Mg atoms), 25Mg (10%), and26Mg (11%); all three are isotopes of Mg (atomic # =12) and are present in all compounds of magnesium in about these same proportions.

Atomic Calculations# of electrons = atomic numberEx: Magnesium (Mg) has _12__ electrons

# of protons = atomic numberEx: Sodium (Na) has _11_ protons

# of neutrons = mass number (atomic mass rounded to nearest whole number) – atomic number

Ex: Tin (Sn) has _69____ neutrons

Atomic Weight, Molecular Weight, & Formula Weight

Atomic Weight- comes from the Periodic Table & is a measure of the average mass of the isotopes of the element

Molecular Weight- is the mass of a molecular compound (water)Ex: H20 = 2 Hydrogen atoms = 2 x 1.01 = 2.02

1 Oxygen atom = 1 x 15.99= 15.99Molecular Weight of water = 18.01 amu

Formula Weight- is the mass of an ionic compound (salt)Ex: NaCl = 1 sodium atom = 22.99 1 chlorine atom = 35.45Formula weight of salt = 58.44 amu

Understanding the Periodic Table

Orbitals (n =2) two electrons can fit inside of one orbital

Sublevels (s,p,d,f)Where s = 1, p = 3, d = 5, f = 7

Energy LevelsRelates directly to # of

horizontal periods in the Periodic Table (1 to 7)

Atomic Apartment BuildingThink of the apartments as only being able to hold two people per room & has 7 floors. Apartment Type # of rooms # of people s 1 2 p 3 6 d 5 10 f 7 14

7

6

5

4

3

2

1 1s

1s2s2p

3s3p

4s3d 4p

5s4d

5p

6s

5d 6p

7s

6d

SublevelsElectron orbital designated as s,p,d,&f

More Terms to understand bondingTerm Definition Example

Cation Positively charged ion Na+1

Anion Negatively charged ion Cl-1

Valence Electrons Electrons in the outermost energy level that can be involved with chemical changes and bonding

Next page

Activity 1: Understanding Periodic Trends

Instructions: Working in groups look at the following charts which show periodic trends for:

1. Atomic radii (atomic size)2. Ionization energy (the measure of energy required to

remove electrons from an atom)3. Electron Affinity (the measure of attraction between

incoming electrons from other atoms and the nucleus of original atom)

Describe what you notice about the charts and what you think they mean.

Write your thoughts in your science journal.

Atomic Radii

Atomic Radii Graph

Ionization Energy

Electron Affinity

Activity # 2 What’s in my cereal?

Materials: Special K cereal & cream of wheat, magnetic stir bar, hot plate, 750 to 1000 mL beaker

Procedure:1. Crush 50 g of Special K flakes with a mortar & pestle2. Fill beaker with 500 mL of water3. Place beaker on hot plate and add a magnetic stir bar, start the

stir function4. Add the crushed flakes to the water and wait 15 minutes5. Remove the magnetic stir bar6. Record your observations in your science journal.7. What do you think is on the stir bar? Check the cereal label to

think about which element you could have extracted from the cereal and explain why you think so.