2. Chemistry

Atoms- Smallest Unit of Matter

Voyage into the world of atoms

Electrons                   .
a. are negatively charged;
b. along with neutrons make up the nucleus;
c. are attracted to the negatively charged nucleus;
d. are not involved in ionic bonds;
e. all of the above are true

Fill in the blanks in this concept map to help you tie together the key concepts concerning elements, atoms, and molecules. <img class="fr-dib" src="https://lightcat-files.s3.amazonaws.com/problem_images/2a24880f1b4d9e7b-1677713945361.jpg" style="width: 300px;">

The reactivity of an atom arises from
a. the average distance of the outermost electron shell from the nucleus.
b. the existence of unpaired electrons in the valence shell.
c. the sum of the potential energies of all the electron shells.
d. the potential energy of the valence shell.

A Better Way To Picture Atoms

A proton ___________:a) Has one positive charge.b) Has one AMU.c) Is found in the nucleus of the atom.d) Only a and b are true.e) a, b, and c are true.

 Carbon, nitrogen, calcium, oxygen, phosphate, iron 

 No. Calcium and iron are important elements for living organisms, but they do not make the list. 

 Carbon, nitrogen, oxygen, calcium, phosphate, hydrogen 

 No. Regardless of what the milk advertisements say, calcium is not on the list. 

 Carbon, nitrogen, sulfur, hydrogen, iron, magnesium 

 No. Iron and magnesium are important trace elements, but they are not on the list. 

 Carbon, nitrogen, oxygen, hydrogen, phosphate, sulfur 

Think about the elements that make up the major functional groups.

What are the six most important chemical elements of life?

Use carbon-12, the most common isotope of carbon, to define these terms: atomic number, mass number, valence. Which of these numbers is most related to the chemical behavior of an atom? Explain.

Atoms- Smallest Unit of Matter Example 1

Look back at the abbreviated periodic table of the elements in Figure 2.5B. If two elements are in the same row, what do they have in common? If two elements are in the same column, what do they have in common? Would you predict that elements in the same row or the same column will have similar chemical properties? Explain. <img class="fr-dib" src="https://lightcat-files.s3.amazonaws.com/problem_images/01fbaa08597c34c3-1677713768393.jpg" style="width: 300px;">

Atoms- Smallest Unit of Matter Example 3

How many valence electrons does an atom with five total electrons have?a) 5.b) 7.c) 3.d) 2.e) 1.

DRAW IT Draw Lewis dot structures for each hypothetical molecule shown below, using the correct number of valence electrons for each atom. Determine which molecule makes sense because each atom has a complete valence shell and each bond has the correct number of electrons. Explain what makes the other molecule nonsensical, considering the number of bonds each type of atom can make. b.

What is an atom? Better explained

We can be sure that a mole of table sugar and a mole of vitamin C are equal in their
a. mass.
b. volume.
c. number of atoms.
d. number of molecules.

 No. Hydrogen plus three other elements accounts for about 96% of living matter. 

 No. Oxygen plus three other elements accounts for about 96% of living matter. 

 No. Nitrogen plus three other elements accounts for about 96% of living matter. 

Trace elements are those required in only minute quantities by most living organisms.

Which of the following is a trace element?

 True. Most organisms have evolved adaptations that allow them to tolerate very high concentrations of trace elements in the environment. 

 No. Elevated concentrations of some trace elements are harmful to many forms of life. 

 True. Only trace element limitation can lead to disease among organisms. 

 False. Increasing the concentration of trace elements above what is required generally has a beneficial effect on organisms. 

 No. Some essential trace elements can be toxic at elevated concentrations in the environment. 

 False. Elevated concentrations of some trace elements such as cobalt and chromium can be toxic. 

Some nonessential elements are known to be toxic to organisms.

If you were told that concentrations of trace elements above what is required by organisms generally have no effect on those organisms, what would you say?

 No. The number of neutrons can differ from the number of protons in a charged or uncharged atom. For example, the different isotopes of an element would have different numbers of neutrons, but each of the different isotopes would have the same number of protons and electrons. 

 No. The number of neutrons determines the isotope, not the number of protons. For example, the different isotopes of an element would have different numbers of neutrons, but each of the different isotopes would have the same number of protons and electrons. 

 equals the number of electrons in the outer orbital of the atom 

 No. The number of protons equals the total number of electrons. The electrons in the outer orbital determine the combining power (valence) of the atom. 

Consider the subatomic particle that has a charge opposite that of a proton.

The number of protons in an uncharged atom __________.

 Hydrogen, oxygen, calcium, and nitrogen 

 No. Calcium is not one of the four most abundant elements found in living systems. 

 No. Sulfur is not one of the four most abundant elements found in living systems. 

 Hydrogen, oxygen, nitrogen, and carbon dioxide 

Consider that the four most abundant elements make up about 96% of living matter.

What are the four most abundant elements found in living systems?

Electron Orbitals & Energy Shells

Add labels to the figure that follows, which illustrates the subatomic particles associated with a carbon atom. <img src="https://lightcat-files.s3.amazonaws.com/problem_images/b3912343711ffd3f-1666097465288.jpg" alt="" /><img class="fr-dib" src="https://lightcat-files.s3.amazonaws.com/problem_images/8954b25fdd5925a3-1677226338646.jpg" style="width: 300px;">

 No. But four elements (carbon, hydrogen, oxygen, and nitrogen) do make up 96% of living matter. 

 No. There are more than 25 naturally occurring elements, but only 25 of them are known to be essential for human life. 

 No. Think of naturally occurring elements. 

An element is a substance that cannot be broken down to another substance by chemical means.

There are __________ naturally occurring elements.

 No. Remember that the innermost or first shell can accommodate only two electrons but the second and third shells can each accommodate up to eight electrons. 

 No. Remember that the third shell can accommodate only a maximum of eight electrons. 

Consider the number of electrons that each shell can accommodate.

A neutral atom of chlorine has an atomic number of 17. It has __________ electrons in its third shell.

Octet Rule

What Is An Atom?

 No. Atomic mass does not consider the number of electrons in an atom. 

 No. Atomic number relates to the number of protons, not to the number of neutrons. Atomic mass does not consider the number of electrons. 

 No. Atomic number relates to the number of protons, not to the number of neutrons. 

What specific subatomic particles contribute to the atomic number and the atomic mass of an atom?

An element has eight protons, nine neutrons, and eight electrons. Its atomic number and atomic mass, respectively, are __________.

In the term trace element, the adjective trace means that
a. the element is required in very small amounts.
b. the element can be used as a label to trace atoms through an organism’s metabolism.
c. the element is very rare on Earth.
d. the element enhances health but is not essential for the organism’s long-term survival.

DRAW IT Draw Lewis dot structures for each hypothetical molecule shown below, using the correct number of valence electrons for each atom. Determine which molecule makes sense because each atom has a complete valence shell and each bond has the correct number of electrons. Explain what makes the other molecule nonsensical, considering the number of bonds each type of atom can make. a. <img src="https://lightcat-files.s3.amazonaws.com/problem_images/3d18a1b7a6c6eda5-1665575355674.jpg" alt="" />

The average oxygen atom has a mass number of 16 and an atomic number of 8. This means that the number of neutrons in this oxygen atom is:a) 24.b) 8.c) 16.d) 4.e) 2.

The number of electrons in a neutral atom is equal to the number of protons in the nucleus of the atom.

How many electrons would be present in the valence shell of a sulfur atom (atomic number 16, mass number 32)?

Structure of an Atom

Changing the _________ would change it into an atom of a different element.
a. number of electrons surrounding the nucleus of an atom
b. number of protons in the nucleus of an atom
c. electrical charge of an atom
d. number of neutrons in the nucleus of an atom

A neon atom (Ne) is unreactive for which of the following reasons?a) It has 7 valence electrons.b) It has 8 valence electrons.c) Its valence shell is full of electrons.&nbsp;d) It has 20 valence electrons.e) b and c only.<img class="fr-dib" src="https://static.studychannel.pearsonprd.tech/courses/biology/thumbnails/b9adee57" style="width: 88px;">

Atoms- Smallest Unit of Matter Example 2

 All organisms require 25 of the 92 naturally occurring elements to survive. 

 No. Humans require 25, but plants need only 17. 

 The elements carbon, hydrogen, nitrogen, and oxygen make up 20&ndash;25% of living mass. 

 No. These elements make up 96% of living matter. 

 Given their low concentrations in nature, the toxicity of some elements is generally not a factor in the evolution of biological communities. 

 No. Certain species of plants have evolved adaptations to survive in soils concentrated with toxic elements, such as seen among the serpentine plant communities.  

 Although all forms of life require iron, other elements are required only by certain species. 

Consider that there is wide variation among organisms in terms of their physical and chemical requirements and tolerances.

What is generally true about essential elements and living organisms?

No. Protons are included in the calculation of atomic mass. A proton weighs about 1.7 &times; 10&ndash;24 grams (atomic mass of about 1 dalton).

No. Neutrons are included in the calculation of atomic mass. A neutron weighs about 1.7 &times; 10&ndash;24 grams (atomic mass of about 1 dalton).

 No. Think subatomic. Atoms are composed of subatomic particles: protons, neutrons, and electrons. 

Consider which of these is not included in the calculation of an atom's atomic mass.

Which of the following has negligible mass?

 No. The number of neutrons cannot be calculated from the provided information. 

The atomic number gives you the information you need to determine the number of protons in an atom.

An uncharged atom of nitrogen (atomic number = 7) has __________.

In what way does the need for iodine or iron in your diet differ from your need for calcium or phosphorus?

Elements of Life

No. A proton weighs about 1.7 &times; 10&ndash;24 grams (has a mass close to 1 dalton), but it has a positive charge.

 No. Electrons have a negative charge and a mass only about 1/2,000 that of a neutron or proton. 

 No. While neutrons are uncharged, protons are positively charged. 

Think about the meanings of the names of the subatomic particles.

Which of the following subatomic particles has appreciable mass but no charge?

Atomic Structure And Electrons - Structure Of An Atom - What Are Atoms - Neutrons Protons Electrons

How many electrons does an Oxygen atom need to fulfill the octet rule by filling its valence shell?a) 8.b) 4.c) 1.d) 2.e) 6.

Atomic Structure

Atomic Properties

They represent regions around the nucleus in which the electrons orbit.

The shells closest to the nucleus contain electrons with higher energy.

They contain electrons of the same energy.

Which of the following is true about electron energy shells?a) They represent regions around the nucleus in which the electrons orbit.b) The shells closest to the nucleus contain electrons with higher energy.c) They contain electrons of the same energy.d) a and b only.e) a and c only.

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