Covalent bonding and molecular geometry

Covalent bonding and molecular geometry

Chemistry

​Have Periodic table and electronegativity chart out

​First, review from yesterday

​

Isotopes, atomic number, atomic mass, molecular formula, empirical formula and Ionic bonding,​

​MOLECULAR FORMULA

​The Octet Rule is important in predicting the chemical formula of simple binary covalent molecular compounds.

Multiple Choice

What is the molecular formula if the empirical formula is CH₂O and the molecular molar mass is 180.18?

• CH₂O
• C₂H₄O₂
• C₄H₈O₄
• C₆H₁₂O₆

Multiple Choice

What is the empirical formula for C₄H₆?

• CH

• CH₃

• C₂H₃

• C₄H₆

Isotopes

• atoms with the SAME number of PROTONS but DIFFERENT number of NEUTRONS

Carbon 12

Consider the Atom Carbon, the atomic number tells us the number of protons.

How many protons in Carbon 12?

Multiple Choice

• The atomic number indicates the number of neutrons

• The atomic number indicates the isotope number

• The atomic number indicates the number of protons

• The atomic number indicates the number of protons and neutrons

Multiple Choice

If you want to determine the total number of protons and neutrons in an atom, you can refer to the

• atomic mass

• atomic number

• symbol

• charge

​Ionic bonding review

What you need to remember... Ionic bonds

• Metals + Nonmetals

• Make IONIC bonds

• Transfer electrons

• High electronegativity difference

Ionic Bonds

• Form Crystalline Lattice (crystals)

• Have high melting and boiling points

• Hard

• Brittle

• Conduct electricity when dissolved in water

Multiple Choice

The positive ions tend to _____________ electrons.

• lose

• gain

Multiple Choice

Ionic bonds are between...

• Metal and Non-metal
• Non-metal and Non-metal
• Metal and Metal

Linear

Trigonal planar

Tetrahedral ​

​Molecular geometry

Main concepts include:

• Sharing of electrons ​

• Electronegativity

• Polar vs. Nonpolar ​

​Covalent bonding

Today's lesson

Some text here about the topic of discussion

What makes this happen? - Chemical bonding

• Electronegativity is the key

• more specifically, the DIFFERENCE in electronegativity....

• ​Electronegativity is the strength that an atom can pull electrons.

ELECTRONEGATIVITY

• DEN Range is the difference in electronegativity values between atoms

• Determines the type of bond

• Covalent bonds have similar electronegativities

• Ionic bonds have different electronegativities

Multiple Choice

Which element has a higher electronegativity value?

• Niobium

• Tin

• Cadmium

• Iodine

Multiple Choice

Which has the greater EN: 
N or C?

• C
• N

Multiple Choice

Put these in increasing order:
C, H, and O

• H < C < O
• H < O < C
• O < C < H
• C < H < O

​Covalent bonding

Key concepts:

• Nonmetal with a nonmetal

• Electrons are being shared

• Polar or nonpolar based on electronegativity of elements bonded

• All elements still want to fill outer shells (octet rule!) ​

Subject | Subject

Some text here about the topic of discussion

Sharing is Caring!

Electrons are shared

What you need to remember - Covalent bonding

• Nonmetal + Nonmetal

• Make COVALENT bonds

• Share electrons

• Low electronegativity difference

Covalent Compounds

• Have Lower melting and boiling points

• Tend to be flammable

• When dissolved in water they do not conduct electricity

• Soft or brittle solid

• Can also form crystals

Multiple Choice

What two types of atoms make a covalent bond?

• 2 Nonmetals
• 1 Nonmetal and 1 Metal
• 2 Metals
• 2 Noble Gases

Multiple Choice

What region of the periodic table contains atoms that form covalent bonds?

• the left side
• the middle
• the right side
• top left

FORMATION OF COVALENT COMPOUNDS

1) The two atoms of nonmetals share valence electrons to obtain the same number of electrons as the nearest noble gas (8 valence electrons) producing molecular covalent compounds.

​Two minutes long

​Hydrogen is special!

​Hydrogen's configuration is 1s¹. S orbital (or first energy level) has a maximum number of valence electrons.

​For the atoms to become stable, they should have a completely filled outer energy level.

Multiple Choice

How many electron/s is/are needed for the hydrogen atom to have a completely-filled last energy level?

• 1

• 2

• 3

• 4

Multiple Choice

How many electrons are needed by oxygen atom to have 8 valence electrons?

• 1

• 2

• 3

• 4

Multiple Choice

What kind of covalent bond is formed between the two oxygen atoms?

• single covalent bond

• double covalent bond

• triple covalent bond

Multiple Choice

What is the chemical formula of the covalent compound that can be formed from nitrogen and hydrogen atom?

• NH₂

• NH₃

• H₃N

Covalent bonding- Polar vs Nonpolar

Some text here about the topic of discussion

Polar vs Nonpolar

• A polar molecule is sharing electrons unequally (two different poles, one positive and the other negative)

• A nonpolar is sharing electrons equally (tug of war with two trucks pulling with the exact same force)

Polar vs Nonpolar

• Polar bonds have a difference in electronegativity that is equal to 0.4 or greater

• Nonpolar bonds have a difference in EN of 0.4 or less

Multiple Choice

What type of bond is I-I

• Polar

• Nonpolar

• Ionic

Multiple Choice

What type of bond is Br-Cl

• Polar

• Nonpolar

• Ionic

Showing Polarity

-The greek letter delta, δ, with a + or – shows the partial charge

-Also an arrow is used pointing towards the more electronegative (therefore slightly negative) element

Molecular Polarity

• Molecular Polarity is different from the polarity of the bonds

• When a molecule is symmetrical it is nonpolar

• A nonsymmetrical molecule is polar

Multiple Choice

Is the molecule Polar or nonpolar?

• Polar

• Nonpolar

Multiple Choice

Is the molecule polar or nonpolar?

• Polar

• Nonpolar

Multiple Choice

Is the molecule polar or nonpolar?

• Polar

• nonpolar

Molecular Geometry

Linear

180° bond angles

Linear Structure (Carbon Dioxide)

Bent (V-Shaped)

< 180° bond angles

Bent / V-Shaped (Sulfur Dioxide)

Trigonal Planar

120° bond angles

Trigonal Planar (Sulfur Trioxide)

Trigonal Pyramidal

< 120° bond angles

Trigonal Pyramidal (Ammonia)

Tetrahedral

109.5° bond angles

Tetrahedral (Methane)

Multiple Choice

Which of the following molecular geometry is possible for carbon tetrachloride?

• linear

• trigonal planar

• tetrahedral

• trigonal pyramidal

Multiple Choice

Which of the following molecular geometry is possible for nitrogen trichloride?

• bent / v-shaped

• trigonal planar

• tetrahedral

• trigonal pyramidal

Multiple Choice

Choose the correct shape for this molecule:

• Tetrahedral
• Trigonal pyramidal
• Bent
• Trigonal planar

Multiple Choice

Choose the correct shape for this molecule:

• Bent
• Linear
• Tetrahedral
• Trigonal pyramidal