Chapter 7: Completing the Model of the Atom

Class Activity (there is no BW)

1. Send 1 student from your team to pick up enough white boards and markers for each person. 1 paper towel per team

2. Draw a Bohr model for the element I assign to you.

Class Activity (there is no BW)

2. Now, find all other students with the same number of occupied energy levels.

• Starting with Hydrogen’s group, stand together. Next, lithium’s group, finally sodium’s group.

• What do you notice?

Class Activity (there is no BW)

3. Now, find all other students with the same number of valence.

• Starting with Hydrogen’s group, stand together. Then, Beryllium’s group, etc.

• Then, boron’s group, etc. What do students notice?

What the Periodic Table Tells Us1. Columns are called “Groups” or “Families”– Main Group Elements are the tall ones!

• Groups 1 & 2, 13-18• They “follow the rules” pretty well. Behavior is predictable.• They tell us how many ______ the atoms of these elements have.• Groups #1&2 – Group # tells you how many • Groups 13-18- subtract 10 from the Group #

– Transition Elements are in between Main Group Elements• Groups 3-12• Behavior is less predictable!

– Inner Transition Elements are at the bottom of the P. Table

What the Periodic Table Tells Us

2. Rows are called “Periods”– They tell us the location of the _______ in atoms

of these elements.

Use the P. Table to Make an e- Diagram for an Element

• Ex: Lithium• Identify its Group #: 1

• Identify its Period #: 2

Q: So how many valence e-s does a lithium atom have? And where are they located?

A: 1 valence e- in the 2nd energy level

Light: Electromagnetic Spectrum• Energy can travel in waves. • There are high energy and low energy waves.• The ones we can see are called “the visible

spectrum.” ROY G BIV• Red is the low energy end: violet is the high

energy end.

Movement of e-’s

• e-s can jump to higher energy levels if they absorb energy.

• They can’t keep the energy so they lose it and “fall back” to lower levels.

• When they do this, they release the energy they absorbed in the form of light.

Movement of e-s, cont.

• When e-s absorb energy, they do so in certain amounts. (They “jump” specific distances.)

• When they release energy, they do so in certain amounts. (They “fall” specific distances.) And they release light that has that amount of energy.

• Question: if e-s fall a long distance, they release a lot of energy. What is the color that is likely to be released? (red end or purple end of spectrum?)

Emission Spectrum

• Def: Each element has a characteristic set of colors that are given off when its e-s “fall back.”

• You can identify an element by its emission spectrum!

• Emission spectrum of hydrogen

Emission Spectrum (cont.)

• See Fig 7.4 on p 235• H has 4 spectral lines (4 colored lines)• Mercury (Hg) has 11 lines! • Ne has 20+ lines!

Problem: there are more lines than you would expect if there are only a few energy levels.

Hypothesis: There must be many sublevels in an energy level

Electron Sublevels

Each electron has an “address,” where it can be considered to be located in the atom.

• Main energy level= “hotel”• Sublevel = “floor”• Orbital = “room” – Regions of space outside the nucleus– All orbitals in a sublevel have the same energy– 2 electrons max can fit in an orbital

Sublevels in Atoms

• See Fig 7.5 on p 235Main energy level

Types of sublevels

# of orbitals # of electrons

1 s 1

2 s p

13 (4 total)

3 s p d

1 3 5 (9 total)

4-7 s p d f

1 3 5 7 (16 total)

Orbitals• s orbitals are spherical– There is only 1 orbital

• p orbitals are dumbbell shaped– There are 3 orbitals, all with = energy– Each is oriented on either x, y, or z axis– They overlap

• d orbitals have varying shapes– There are 5 orbitals, all with = energy

• f orbitals have varying shapes– There are 7 orbitals, all with = energy

Electron Configurations

• Electrons are always arranged in the most stable (lowest energy) way

• This is called“electron configuration”

Section 2: The Periodic Table & Atomic Structure

• Shape of p. table is based on the order in which sublevels are filled

REGIONS OF THE P. TABLE (see p 244 of book)• s REGION (“block”) - Groups 1 & 2• p REGION (block) - Groups 13-18• d REGION (block)- Groups 3-12 (Transition

Elements)• f REGION (block)- (Inner Transition Elements)

List sublevels from lowest to highest energy level (Using

P.Table)1. Always start with Period 1-go from L to R.2. Go to Period 2-from L to R3. Go to Period 3- from L to R4. Continue 4-7 periods, L to R until you have

completed the P. Table.• Exception: elements in d block are 1 main E.L lower

than the period where they are located• Exception: elements in f block are 2 main E.L.s

lower than the period in which they are located

Correct Order of Sublevels (lowest to highest energy)

• 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p

Why Exceptions w/d & f block elements?

• When you get to the higher main E.L.’s, the sublevels begin to overlap.

E- configurations

• Use the P. Table to write the sublevels in increasing order, as previously instructed.

• Add a superscript next to each sublevel that shows how many e-s are in the sublevel

• Ex: Oxygen: 1s22s22p4

Valence e-s

• Valence e-s are the electrons in the highest occupied main energy level.

• Identify the valence e-s by finding the “biggest big number” in your e- configuration.Ex: Oxygen: 1s22s22p4

Question: WHAT IS THE BIGGEST BIG NUMBER YOU SEE? WHAT ARE THE VALENCE ELECTRONS?

Noble Gas Notation

• Short-cut way of showing e- configuration• A Noble Gas is a Group 18 element.1.Identify the noble gas in the period above your

element of interest. Write this symbol in brackets.2.Write the e- configuration for any additional e-s

that your element of interest has, but the noble gas doesn’t have.

Ex: Nitrogen: 1s22s22p5 becomes [He] 2s22p5

Practice Noble Gas Notation

• Tungsten (W)• E- configuration

• Noble Gas configuration

Arrow Orbital Diagram-Used to show e- configuration.

SYMBOLS:• A box represents an orbital– Label each box with the sublevel :1s 2s 2p

2p 2p

• An arrow represents an electron– 2 arrows (e-s) in the same orbital face opposite

directions.– Example: oxygen, see above

↑ ↓ ↑ ↓ ↑ ↓ ↑ ↑

Arrow Orbital Diagram-Used to show e- configuration.

INSTRUCTIONS:• Fill electrons from lowest to highest sublevel.• Never place 2 e-s in the same orbital of a

sublevel until you have placed one in each of the orbitals

Arrow Orbital Diagram: Practice

Regions or “Blocks” of the P. Table