Valence Electrons and Electron Configuration

Explaining the arrangement of electrons

08/27 & 08/28

Catalyst• Take out your HW to be stamped.• On your Daily Work Organizer, fill

in your goal for the week.• Catalyst: Describe the pictured

substances.

Video Clip: Reviewhttp://www.youtube.com/watch?v=1PSzSTilu_s&feature=bf_prev&list=PL65159266CFC74682

Homework BaseballAnswer the questions on a blank

sheet of paper. Use your homework.

1. Why are the noble gases the least reactive elements?

2. In the electron configuration 1s2, the 1 represents the:

(a) number of protons (b) number of electrons (c) the energy level

Homework Baseball: Answers

1. Why are the noble gases the least reactive elements? They have a full shell of valence electrons.

2. In the electron configuration 1s2, the 1 represents the:

(a) number of protons (b) number of electrons (c) the energy level

Objectives

• SWBAT draw Lewis dot diagrams.• SWBAT write electron configurations.• SWBAT explain the octet rule and use

it to predict ion formation.

Agenda

• Catalyst• Electrons and Intro to Ions• Mystery Elements Puzzle• Exit Ticket

Properties of the atom

• Protons determine the physical properties– The number of protons makes the

element• Electrons determine the chemical

properties– Only the electrons react!!!

Electron Energy Levels• In the electron cloud, electrons are arranged

in energy levels (aka orbitals or shells). • Electrons fill the levels from the inside out.• Electrons in the outer shell form chemical

bonds (react) with other atoms.

1

2

3

4

5

6

7

Write: periods tell us energy levels

What are valence electrons??

• Valence electrons are electrons on the outer shell of an atom that are available for bonding.

– Valence Electrons are VERY IMPORTANT, they determine an element’s reactivity and general characteristics

1 23 7654 8

Write: groups tell us # valence electrons

Practice: Draw the Bohr model and Lewis Dot Structure for N, O, F, Ne,

Na, and Mg.Note: 1st orbital has 2 e, 2nd and 3rd orbitals

have up to 8 e.• Lewis Dot

symbols show us how many valence electrons are in an atom.

• Bohr models show us all the electrons, separated by energy level (orbital).

Li

Ions!• Octet Rule: When forming ions,

atoms give or take electrons in order to have a full outer orbital (or shell).– They end up with the same number

of electrons as the closest noble gas. This is usually 8. (Exception: Helium with 2.)

Think, pair, share.

• How many electrons would N, O, F, Na, & Mg lose or gain to have the same number of electrons as Ne?

• What ions are formed?• Example: Lithium loses 1 e to

form Li+ (same # e as He)(Work with the person next to you

and write your answers under your Lewis Dot structures in your notes.)

Ions! Cations and Anions• Ion = an atom that has gained or

lost electrons – Ions have a negative or positive

charge.

• Anion = ion with a negative charge.– Usually nonmetals

• Ex: Cl- S2-

• Cation = ion with a positive charge.– Usually metals

• Ex: Be2+ Al3+

Think, Pair, Share

• Are the ions of N, O, F, Na, and Mg cations or anions?– Label them in your notes.– Then share with your partner.

• Does Ne form an ion? Why not?

Electron Configuration

• A way to keep track of all those electrons!

• Write this down:

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6

http://www.youtube.com/watch?v=Vb6kAxwSWgU

© 1998 by Harcourt Brace & Company

S orbital P orbital

D orbital

F orbital

1234567

67

Within the Energy Levels, electrons are arranged in 1 or

more orbitals. Label the orbitals on your periodic table.

Orbitals

S

p d f

Each orbital within a level has:• different energies• different shapes• Different orientation in space

s-block

1st Period

1s1# e- in sublevel

1 2 3 4 5 6 7

Periodic Table &

Electron Configuration• Example - Hydrogen

1 2 3 4 5 6 7

p-block

2nd Period

1s22 e- in p sublevel

• Example - Carbon

2s22p2

XXX

XXX

Periodic Table & Electron Configuration

1 2 3 4 5 6 7

p-block

2nd Period

[He]

Short Hand Configuration

• Example - Carbon

2s22p2

XXX

XXX

S 16e-

Valence Electrons(Outer shell)

Core Electrons (Inner orbitals)

1s2 2s2 2p6 3s2 3p4

Notation

• Longhand Configuration

Let’s Try It!• 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6

Practice! Write the electron configuration for the following elements:N, O, F, Ne, Na, Mg

Write your answers under your Bohr models and Lewis Dot Structures for these elements.

Agenda

• Catalyst• Electrons and Intro to Ions• Mystery Elements Puzzle• Exit Ticket

Mystery Elements Puzzle

• Work in a group of 4 at your table• Use the clues and your periodic

table to match each symbol with an element.

• Write down your answers on a sheet of paper.

• Raise your hand when you think you have solved the puzzle.

Exit Ticket

1. Draw the Bohr model and Lewis Dot Structure for Phosphorus (P).

2. Write the electron configuration of P.

3. How many electrons will P lose or gain to form an ion? How do you know?

4. What ion does P form? Is it an anion or cation?

If you are done, work on HW packet.