Chemistry Unit 4: Bonding Essential question: How are electrons arranged in orbitals?

Where are electrons found? Electrons do not travel in specific orbits as in Bohr’s Model of the atom Instead, they travel within the atomic orbitals

What are atomic orbitals? These are regions where there is a high probability of finding an electron Each atomic orbital has a principal energy level denoted by the letter, (n).

Principal Energy Levels can be broken down into Sublevels with different shapes called orbitals.

Electrons in atoms are arranged as: Summary Electrons in atoms are arranged as: LEVELS (n) SUBLEVELS ORBITALS

Sublevels are written as 1s, 2s, 2p…….

What are the 4 types of orbitals? There are the s, p, d and f orbital.

S orbitals Spherical shaped # of s orbitals: 1 Can hold a max. of 2 electrons

P orbitals # of p orbitals: 3 Dumbbell shaped Can hold a maximum of 6 electrons

The d sublevel contains 5 D orbitals The d sublevel starts in the 3rd energy level 5 different orbitals Can hold a max. of 10 electrons

The f sublevel has 7 F orbitals The F sublevel starts in the fourth energy level seven different orbitals Can hold a max of 14 electrons

Electrons in atoms are arranged as: Summary Electrons in atoms are arranged as: LEVELS (n) SUBLEVELS ORBITALS

Summary 2 6 10 14 s p d f 1 3 5 7 Maximum electrons # of shapes (orbitals) Starts at energy level #of pigs Rooms in Hotel 2 s 1 1 p 3 6 2 10 d 5 3 7 14 4 f

How are electrons filled in orbitals? There are three rules to follow: Aufbau principle - electrons enter the lowest energy first. Hund’s Rule- electrons don’t pair up until they absolutely have to. Pauli Exclusion Principle - at most 2 electrons per orbital. If they must pair up they have different spins (face opposite directions).

So how do we write this? We use an orbital diagram.

So how do we write this? It can also be written in a straight line just like your Hog Hilton activity Like this, 1s 2s 2p 3s 3p

How do we know which sublevel to place an electron in? You must determine how many electrons to fill in your orbitals. Use the periodic table, of course! And the three electron filling rules!

s p d f 1 2 3 4 5 6 7 1A 2A 3B 4B 5B 6B 7B 8B 1B 2B 3A 4A 5A 6A 7A 8A Row = # shells d f

# of electrons in orbital Orbital Diagrams 1s Period # # of electrons in orbital subshell possibilities are s, p, d, or f

Example Orbital diagram of Carbon

Lets try Neon together!

On your own, Draw the orbital diagram for Sulfur

Work with a partner! Draw the orbital diagram for Potassium.

Work with a partner! Draw the orbital diagram for Nickel.

It is called electron configuration Easier way? It is called electron configuration

Describe how to write the electron configuration for an atom. OBJECTIVES: Describe how to write the electron configuration for an atom.

s p d f 1 2 3 4 5 6 7 1A 2A 3B 4B 5B 6B 7B 8B 1B 2B 3A 4A 5A 6A 7A 8A Row = # shells d f

Electron Configuration 1s1 possibilities are: s: 1 or 2 p: 1-6 d: 1-10 f: 1-14 Period # subshell possibilities are s, p, d, or f What element has an electron configuration of 1s1?

For example, Orbital diagram of carbon Electron configuration of Carbon is 1s²2s²2p² Simply count electrons as you fill each orbital!

Let’s Practice together Let’s write the electron configuration for Phosphorus 1s²2s²2p⁶3s²3p³

On your own, Write the electron configuration for Calcium 1s²2s²2p⁶3s²3p⁶4s²

On your own, Write the electron configuration for Iron 1s²2s²2p⁶3s²3p⁶4s²3d⁶

Which element is this? The total number of electrons at the top helps you to identify the element!

With an elbow buddy, complete The Electron Configuration Station Activity

Warm Up Give the Lewis Dot Structure for the following: Chlorine Calcium Gallium Carbon Sulfur

What is the “ground state” of an atom? This is the normal electron configuration of atoms. This is the most stable state for electrons

What is the “excited state” of an atom? This happens when electrons are heated and they absorb the heat energy. Because of the extra energy, electrons are able to ‘jump’ to higher energy levels. This is known as the “excited state”.

What happens in the “excited state”? In this state, electrons are unstable, so they fall back to their lower energy levels. As they return to their lower energy level, the energy absorbed gets released as light. The visible light is called a photon or a quanta of light.

Photons? The color of this photon is used to identify elements. Such analysis is done using a Flame Test.

What is the electron emission spectrum? The color emitted by each element can be used to identify an element, similar to a fingerprint.

What are valence electrons? What is the octet rule?

Valence Electrons Valence electrons are the electrons located in the outermost orbit Elements become stable when: their outer orbit contains 8 electrons or their outer orbit becomes empty Lewis Dot Diagrams show the # of Valence Electrons

Octet Rule? Atoms can gain, lose, or share electrons until they have eight valence electrons.

Part 2:Essential questions: Why do atoms bond? How are bonds formed?

Forces that hold groups of atoms together and make them function as a unit. What are bonds?

What are the two main types of bonds? Ionic bonds 2) Covalent bonds

What are Ionic bonds? Form between a metal and a nonmetal Metals transfer electrons to the non-metal

Ionic bond video clip http://youtu.be/QqjcCvzWwww

What are the properties of ionic compounds? High melting points High boiling points Conduct electric current when dissolved in solution Difficult to break

For example

Ionic Bonds What is the formula for the compound that forms between magnesium and chlorine? Cl · · · Mg · · Cl · · · MgCl2 NaCl

Warm Up Give the electron configuration for Strontium What is an Ionic Bond?

Ionic bonds? After bonding, each atom has a full outermost shell with eight valence electrons Except Hydrogen, which needs two valance electrons to be stable and happy!

What are Covalent bonds? This is a bond between two Nonmetals. They share valence electrons with each other. By sharing, both atoms obtain eight valence electrons. They do not give away electrons to bond.

Covalent bonding video clip http://youtu.be/QqjcCvzWwww

How many valence electrons does Fluorine have? Fluorine has seven valence electrons F

F F Covalent bonding Fluorine has seven valence electrons A second atom also has seven F F

F F Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons… …both end with full orbitals and eight valence electrons F F 8 Valence electrons

F F Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons… …both end with full orbitals F F 8 Valence electrons

How do we know a compound is covalent? Two non-metals bonded together Low melting and boiling points Commonly referred to as Molecular Compounds.

H O Water Each hydrogen has 1 valence electron Each hydrogen wants 1 more The oxygen has 6 valence electrons The oxygen wants 2 more They share to make each other complete O

H O H Water A second hydrogen attaches Every atom has full energy levels Note the two “unshared” pairs of electrons H O H

What is the formula for Water? Use the Lewis Dot diagram H2O

How do we show 2 atoms sharing? We use a line It is called a single bond Only one pair of electrons are shared

Sometimes more than one pair of electrons are shared to obtain a full outermost orbit

What if 2 pairs of electrons are shared? We use 2 lines O2

3 electron pairs? We use three lines N2

What is a lone pair? These are the pairs of electrons that are not involved in bonding

What is the central atom? The least electronegative atom The atom that is placed in the center

Warm Up What is a Covalent molecule?

What are the shapes of covalent bonds? Linear Bent Trigonal Planar Tetrahedral Pyramidal

Linear? All electrons in the central atom are bonded Everything is in a straight line

Bent? There are 2 pairs of lone pairs on the central atom

Trigonal Planar? 3 atoms bonded to the central atom

Pyramidal? One lone pair and three bonded sides

Tetrahedral? Four bonded sides around the central atom No lone pairs

How to predict the shape of a molecule? Step 1: Draw the Lewis Dot structure for each atom Step 2: Arrange the elements so that each atom will have a full outmost shell Step 3: Count the number of bonds and lone pairs (if any).

Step 1: Lewis Dot Structure Let’s try together! NH3 Step 1: Lewis Dot Structure Step 2: Arrange atoms Step 3: Count the number of bonds and lone pairs 3 bonds and one lone pair Pyramidal

On your own Predict the shape of CH4 Tetrahedral

With a partner! Predict the shape of H2S CCl4 CHCl3

What is a polar molecule? A molecule where electrons are shared unequally. What is a Non-polar molecule? A molecule where electrons are shared equally.

How do we know if a molecule is polar? If the central atom has LONE pairs, it is a POLAR molecule

How do we know if a molecule is non-polar? If there are NO lone pairs present on the central molecule, it is NON-POLAR.

Exit ticket Predict the shape of BF3