introduction to chemical bonds

kqed the sweet science of chocolate

Chocolate: Its been revered for millennia by cultures throughout the world. But while its easy to appreciate all of its delicious forms, creating this confection is a complex culinary feat. Local chocolate makers explain the elaborate engineering and chemistry behind this tasty treat. And learn why its actually good for your health! For more information on the science of chocolate, see http://science.kqed.org/quest/video/the-sweet-science-of-chocolate/ . MEDIA Click image to the left or use the URL below. URL:

types of compounds

There are different types of compounds. They differ in the nature of the bonds that hold their atoms together. The type of bonds in a compound determines many of its properties. Three types of bonds are ionic, covalent, and metallic bonds. You will read about these three types in later lessons. You can also learn more about them by watching this video: (7:18). MEDIA Click image to the left or use the URL below. URL:

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same elements different compounds

The same elements may combine in different ratios. If they do, they form different compounds. Figure 7.2 shows some examples. Both water (H2 O) and hydrogen peroxide (H2 O2 ) consist of hydrogen and oxygen. However, they have different ratios of the two elements. As a result, water and hydrogen peroxide are different compounds with different properties. If youve ever used hydrogen peroxide to disinfect a cut, then you know that it is very different from water! Both carbon dioxide (CO2 ) and carbon monoxide (CO) consist of carbon and oxygen, but in different ratios. How do their properties differ?

chemical compounds

Water (H2 O) is an example of a chemical compound. Water molecules always consist of two atoms of hydrogen and one atom of oxygen. Like water, all other chemical compounds consist of a fixed ratio of elements. It doesnt matter how much or how little of a compound there is. It always has the same composition.

chemical formulas

Elements are represented by chemical symbols. Examples are H for hydrogen and O for oxygen. Compounds are represented by chemical formulas. Youve already seen the chemical formula for water. Its H2 O. The subscript 2 after the H shows that there are two atoms of hydrogen in a molecule of water. The O for oxygen has no subscript. When there is just one atom of an element in a molecule, no subscript is used. Table 7.1 shows some other examples of compounds and their chemical formulas. Name of Compound Electron Dot Diagram Numbers of Atoms Chemical Formula Name of Compound Hydrogen chloride Electron Dot Diagram Numbers of Atoms H=1 Cl = 1 Chemical Formula HCl Methane C=1 H=4 CH4 Hydrogen peroxide H=2 O=2 H2 O2 Carbon dioxide C=1 O=2 CO2 Problem Solving Problem: A molecule of ammonia consists of one atom of nitrogen (N) and three atoms of hydrogen (H). What is its chemical formula? Solution: The chemical formula is NH3 . You Try It! Problem: A molecule of nitrogen dioxide consists of one atom of nitrogen (N) and two atoms of oxygen (O). What is its chemical formula?

chemical bonding

Elements form compounds when they combine chemically. Their atoms join together to form molecules, crystals, or other structures. The atoms are held together by chemical bonds. A chemical bond is a force of attraction between atoms or ions. It occurs when atoms share or transfer valence electrons. Valence electrons are the electrons in the outer energy level of an atom. You can learn more about chemical bonds in this video: MEDIA Click image to the left or use the URL below. URL: Look at the example of water in Figure 7.1. A water molecule consists of two atoms of hydrogen and one atom of oxygen. Each hydrogen atom has just one electron. The oxygen atom has six valence electrons. In a water molecule, two hydrogen atoms share their two electrons with the six valence electrons of one oxygen atom. By sharing electrons, each atom has electrons available to fill its sole or outer energy level. This gives it a more stable arrangement of electrons that takes less energy to maintain.

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instructional diagrams

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Water is a transparent common substance that makes up the earth's oceans, lakes, seas, rivers, streams and more. Water is essential for every living thing to replenish and hydrate. The chemical formula for water contains one oxygen atom to two hydrogen atoms. Everything from the earth's crust to the human brain contain great amounts of water. Water on earth is continually being used and then goes through the water cycle to become new and usable again. The water cycle involves evaporation, transpiration, condensation, precipitation and runoff. Even though water does not have any calories or nutritional benefit it is essential to all living forms on earth. Fishing which occurs in salt and fresh type waters yields much food for the world's people. Water even involves exercise for those who like to swim and engage in other sports like water skiing, wakeboarding and so on.

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This image shows the chemical structure of Acetylene. Acetylene is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. As an alkyne, acetylene is unsaturated because its two carbon atoms are bonded together in a triple bond. The carboncarbon triple bond places all four atoms in the same straight line, with CCH bond angles of 180.

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The diagram shows the Lewis Dot Structure of Carbon. Lewis Structures are visual representations of the bonds between atoms and illustrate the lone pairs of electrons in molecules. The electrons in the outermost electron shell are called valence electrons. These electrons have an essential role in chemical bonding. Lewis Structures can also be called Lewis dot diagrams and are used as a simple way to show the configuration of atoms within a molecule. In constructing a Lewis Structure, an element is represented by a Lewis symbol (e.g. C for Carbon). It is surrounded by dots that are used to represent the valence electrons of the element. Lewis symbols differ slightly for ions. When forming a Lewis symbol for an ion, the chemical symbol is surrounded by dots that are used to represent valence electrons, and the whole structure is placed in square brackets with superscript representing the charge of the ion.

questions

Subscripts in a chemical formula are used to show the number of

a. molecules in a substance.

-->  b. atoms of each element in a compound.

c. different elements in a compound.

d. protons in an element.

There are millions of unique substances in the universe because elements can combine in many different ways to form

a. mixtures.

b. solutions.

-->  c. compounds.

d. ions.

Which chemical formula represents the compound hydrogen peroxide?

a. H2 O

b. HO2

-->  c. H2 O 2

d. H2 O 3

Water is an example of a(n)

a. unique substance.

b. chemical compound.

c. covalent compound.

-->  d. all of the above

The chemical formula HCl represents the compound named

-->  a. hydrogen chloride.

b. hydrogen carbide.

c. methane.

d. none of the above

Which statement is true about water and hydrogen peroxide?

a. Both substances have the same properties.

b. Both substances have the same chemical formula.

-->  c. Both substances consist of hydrogen and oxygen.

d. Both substances are mixtures of elements.

Chemical bonds always involve

a. ions.

b. atoms.

c. metals.

-->  d. electrons.

Which statement is true about carbon dioxide and carbon monoxide?

-->  a. Both compounds consist of carbon and oxygen.

b. Both compounds have all the same properties.

c. Both compounds are harmless gases.

d. all of the above

How many valence electrons does an oxygen atom have?

a. 2

b. 4

-->  c. 6

d. 8

The ratio of elements in a given compound

a. is always 2 to 1.

-->  b. is always the same.

c. may vary.

d. two of the above

A given compound always has the same

a. chemical formul

b. composition.

c. volume.

-->  d. two of the above

When there is just one atom of an element in a molecule, what subscript is used for the element?

a. 1

b. 0

c. 2

-->  d. No subscript is use

An oxygen atom has eight valence electrons.

a. true

-->  b. false

A molecule of carbon monoxide has two carbon atoms and one oxygen atom.

a. true

-->  b. false

The types of bonds in chemical compounds determine many of their properties.

-->  a. true

b. false

The same elements may form different compounds.

-->  a. true

b. false

The chemical formula for carbon dioxide is CO2 .

-->  a. true

b. false

A hydrogen atom has two electrons.

a. true

-->  b. false

Each element is represented by a unique chemical formula.

a. true

-->  b. false

The compound carbon dioxide has twice as many oxygen atoms as carbon atoms.

-->  a. true

b. false

The same elements may combine in different ratios to form the same compound.

a. true

-->  b. false

Any molecule that contains only hydrogen and oxygen is water.

a. true

-->  b. false

Different types of compounds differ in the types of bonds that hold their atoms together.

-->  a. true

b. false

Both coal and diamond consist of atoms of carbon that are bonded together.

-->  a. true

b. false

Most of the unique substances on Earth are compounds.

-->  a. true

b. false

When atoms combine chemically they form mixtures.

a. true

-->  b. false

A chemical bond consists of matter that connects two different atoms.

a. true

-->  b. false

pure substance that cannot be separated into any other substances

a. chemical bond

b. chemical formula

c. compound

d. valence electron

-->  e. element

f. molecule

g. ionic

unique substance that forms when elements combine chemically

a. chemical bond

b. chemical formula

-->  c. compound

d. valence electron

e. element

f. molecule

g. ionic

particle of a compound that forms when atoms bond together

a. chemical bond

b. chemical formula

c. compound

d. valence electron

e. element

-->  f. molecule

g. ionic

one of three types of chemical compounds

a. chemical bond

b. chemical formula

c. compound

d. valence electron

e. element

f. molecule

-->  g. ionic

symbol representing a chemical compound

a. chemical bond

-->  b. chemical formula

c. compound

d. valence electron

e. element

f. molecule

g. ionic

particle in the outer energy level of an atom

a. chemical bond

b. chemical formula

c. compound

-->  d. valence electron

e. element

f. molecule

g. ionic

force of attraction between atoms or ions that share or transfer electrons

-->  a. chemical bond

b. chemical formula

c. compound

d. valence electron

e. element

f. molecule

g. ionic

diagram questions

question_image

What letter is used inside the Carbon symbol?

a. B

-->  b. C

c. A

d. D

question_image

How many carbons are in the image?

a. 4

b. 2

-->  c. 1

d. 3

question_image

How many covalent bonds does Bromine form?

-->  a. 1

b. 3

c. 2

d. 4

question_image

What is another way this hydrocarbon compound could be expressed?

a. CH4C

-->  b. C2H4

c. H4C2

d. CH2CH2

question_image

What links the carbon atoms?

a. mighty bond

b. physical bond

-->  c. covalent bond

d. chemical bond

question_image

How many electrons has an ethylene molecule?

a. 4

b. 10

c. 8

-->  d. 12

question_image

How many hydrogen bonds are there with Carbon?

a. 4

b. 5

c. 6

-->  d. 2

question_image

How many hydrogen atoms does ethylene have?

a. 6

b. 8

-->  c. 4

d. 2

question_image

How many bonds do F have with B?

-->  a. 6

b. 7

c. 2

d. 4

question_image

The name of this molecule is?

a. bfff

-->  b. BF3

c. FBFF

d. 3FB

question_image

According to the diagram, how protons does the Hydrogen atom have?

a. 2

-->  b. 1

c. 3

d. 4

question_image

What symbol is for Hydrogen?

a. Ho

b. Hy

c. He

-->  d. H

question_image

How much hydrogen atom is there?

a. 2

b. 3

c. 4

-->  d. 1

question_image

How many lone pair/s of electrons does oxygen have?

a. 3

b. 6

c. 4

-->  d. 2

question_image

How many dots are contained in this image?

a. 5

b. 4

-->  c. 6

d. 2

question_image

How many electrons does oxygen have?

-->  a. 6

b. 5

c. 7

d. 8

question_image

How many electrons are shared between oxygen and hydrogen atoms?

a. 2

-->  b. 4

c. 6

d. 8

question_image

How much Oxygen atom is shown in the diagram?

a. 2

b. 4

c. 3

-->  d. 1

question_image

How many oxygen ions bond with Hydrogen?

a. 3

b. 4

c. 1

-->  d. 2

question_image

How many black circles are around the Cl?

a. 5

b. 7

c. 6

-->  d. 8

question_image

How many electrons are there in the diagram?

a. 6

b. 4

c. 2

-->  d. 8

question_image

How many atoms of carbon there are?

-->  a. 2

b. 3

c. 4

d. 1

question_image

How many free-floating electrons are shown in this chemical compound?

-->  a. 4

b. 1

c. 2

d. 6

question_image

How many valence electrons are in the picture?

a. 10

-->  b. 4

c. 6

d. 2

question_image

How many valence electrons does aluminum have?

a. 2

b. 0

-->  c. 3

d. 1

question_image

How many protons does Chlorine have?

a. Five

b. Six

c. Two

-->  d. Seven

question_image

How many unpaired electrons does chlorine atom have?

-->  a. 1

b. 7

c. 3

d. 2

question_image

Which lesson is this symbol used in?

a. Foreign languages

b. English

-->  c. Science

d. Math

question_image

Which represents the atom of Hydrogen?

a. both

-->  b. image on the right

c. left image

d. none

question_image

How many electrons does a Hydrogen atom have?

a. 5

-->  b. 1

c. 2

d. 7

question_image

How many valence electrons does a carbon atom have?

a. 2

-->  b. 4

c. 8

d. 1

question_image

How many atoms of Carbon are in the diagram?

-->  a. 2

b. 5

c. 8

d. 4

question_image

How many electrons are there in the carbon to carbon bond?

-->  a. 4

b. 2

c. 6

d. 3

question_image

The representation of acetylene shows that carbon has what type of bond?

-->  a. triple

b. double

c. quadruple

d. single

question_image

How many black dots are on the following object?

a. 6

b. 12

-->  c. 10

d. 8

question_image

How many bonds are formed between C atoms in Acetylene?

a. 2

b. 4

-->  c. 3

d. 1

question_image

How many protons does H20 have?

a. 9

b. 6

-->  c. 8

d. 4

question_image

How many electrons are there in a water molecule?

a. 4

b. 6

-->  c. 8

d. 2

question_image

How many oxygen atoms does the water molecule have?

a. 0

b. 3

c. 2

-->  d. 1