Link to Chemistry for Biology Students: Study Guide/Student Worksheet

Atoms (Basic Chemistry Tutorial 1) focused on the general structure of atoms. Here, you’ll learn how to determine an atom’s specific structure, which will set us up for learning about chemical bonds in the next tutorials.

If you’ve already watched the video, Click here, or scroll down below the video to start interacting.

 

1. Drawing the Simplest Atoms: Hydrogen and Helium

The most common element in the universe is hydrogen, a gas which makes up about 99% of the universe’s known mass1. Hydrogen is the main component of stars, and a star is, by far the most massive thing in any solar system.

1 That’s not including “dark matter,” which is beyond the scope of this course.

 Hydrogen atoms have one proton, and one electron. So we can represent hydrogen like this:

Hydrogen: One proton and one electron. The arrow points to the first energy level.

Hydrogen has one single proton that goes in the nucleus. Outside the nucleus orbits a single electron, which is found in the first energy level.

[qwiz style = “width: 528px; min-height:0px; border: 3px solid black; ” qrecord_id=”sciencemusicvideosMeister1961-Drawing Atoms, Predict Helium”]

[h]Predict!
[q]Helium is the second most common element in the universe. Helium atoms have two protons, two neutrons, and two electrons. See if you can extend what we’ve learned so far to draw a diagram of helium. After you’ve drawn it, click “show the answer” to see if you drew it correctly.

[c*] show the answer

[f] ANSWER

Helium: 2 protons, 2 neutrons, and 2 electrons
Helium: 2 protons, 2 neutrons, and 2 electrons. The arrow points to the first energy level.

In helium, two protons and two neutrons are found in the nucleus. Two electrons orbit outside the nucleus, in the first energy level (also called a “shell” or “orbit”). Note that the term “orbital,” used in the accompanying video, has a slightly more technical meaning, and we’ll be avoiding it here.

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Make sure you’ve clicked “show the answer” and studied the diagram above before proceeding.

2. The Octet Rule

For atoms with more than two protons and two electrons, a few rules need to be introduced in order to diagram them in a way that represents their chemical properties.1

1When you learn about atoms in a chemistry class, you’ll learn a much more sophisticated and accurate model of electron arrangement. But for the biology that you’ll learn in an introductory high school (or even college) course, the rules that follow will work.

The first rule is called the Octet Rule. “Octet” refers to eight electrons, as you’ll see below. The key parts of the rule are:

  1. Each of the energy levels where electrons are found has a fixed capacity to hold electrons.
  2. The first energy level can hold up to two electrons.
  3. The second and third energy levels can hold up to eight electrons (hence, “Octet”).
  4. When one energy level is filled, you start filling the next one.

Let’s use the Octet Rule to draw a lithium atom.

[qwiz style = “width: 528px; min-height:0px; border: 3px solid black; ” qrecord_id=”sciencemusicvideosMeister1961-Drawing Atoms, Predict Lithium”]

[h]Predict!
[q]Lithium is a metallic element that has 3 protons, 4 neutrons, and 3 electrons. The first two electrons go into the first energy level. With the first energy level filled, the next electron goes into the second energy level. Use the description of the Octet Rule to draw a diagram of lithium. After you’ve drawn it, click “show the answer” to see if you drew it correctly.

[c*] show the answer

[f] ANSWER

Lithium: 3 protons, 4 neutrons, and 3 electrons

In lithium, three protons and four neutrons are found in the nucleus. Two electrons orbit outside the nucleus, in the first energy level (also called a “shell”). The third electron goes into the second energy level.

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Make sure you’ve clicked “show the answer” and studied the diagram above before proceeding.

From this point on we’re going to simplify our diagrams by drawing the nucleus differently.

  • Instead of showing individual protons and neutrons, draw a circle to indicate the nucleus.
  • Write the number of protons and neutrons inside the circle.

Below on the left, you can see this new representation of lithium, next to the one we’ve previously used.

Lithium: 3 protons, 3 neutrons, 3 electrons
Lithium: 3 protons, 3 neutrons, 3 electrons

Lithium: 3 protons, 4 neutrons, and 3 electrons
Lithium: 3 protons, 3 neutrons, 3 electrons
New representation of lithium (notice how protons and neutrons are indicated in the nucleus) Previous representation of lithium showing individual protons and neutrons

To represent the atoms of the next few elements, we need one more rule: place the electrons in the energy level singly until you have four, and then pair them up until you have filled the energy level with 8 electrons. As we’ll see, this rule will help you to understand what’s happening when we learn about chemical bonding, where electrons trade or share electrons. Following that rule, we can draw the next atoms, all the way through neon.

[qwiz style = “width: 528px; min-height:0px; border: 3px solid black; ” qrecord_id=”sciencemusicvideosMeister1961-Drawing Atoms, Predict B, C, and N”]

[h]Predict!
[q]Using what you know about the Octet Rule, draw three more atoms

  • Boron: 5 protons, 6 neutrons, 5 electrons
  • Carbon: 6 protons, 6 neutrons, 6 electrons
  • Nitrogen: 7 protons, 7 neutrons, 7 electrons

After you’ve drawn them, click “show the answer” to see if you drew them correctly.

[c*] show the answer

[f] ANSWER

Boron

Carbon

Nitrogen

Two electrons go in the first energy level. The next three go into the second energy level. Each outer electron is unpaired. Two electrons go in the first energy level. The next four go into the second energy level. Each outer electron is unpaired. Two electrons go in the first energy level. The next five go into the second energy level. One of the outer electrons has to be paired up.

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Make sure you’ve studied the answer to the problem above before going on.

2a. Elements 3 through 10 (Lithium through Neon)

The table below shows all the atoms in the second row of the Period Table of the Elements. Study it and make sure that the arrangement of electrons makes sense to you before going on.

26_second orbital images

2b. Elements 11 through 20

If the number of electrons in an atom exceeds 10 (the limit of the first two energy levels), then the next electrons go into the third energy level. The rules for filling the third energy level are exactly the same as those described above.

[qwiz style = “width: 528px; min-height:0px; border: 3px solid black; ” qrecord_id=”sciencemusicvideosMeister1961-Drawing Atoms, Predict Aluminum”]

[h]Predict!
[q]Aluminum has 13 protons, 14 neutrons, and 13 electrons. Use the description of the Octet Rule to draw a diagram of aluminum. After you’ve drawn it, click “show the answer” to see if you drew it correctly.

[c*] show the answer

[f] ANSWER

Aluminum

To draw aluminum, put two electrons in the first energy level. The next eight go into the second energy level. The remaining 3 electrons go into the third energy level.

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Here are elements 10 through 18, which are the ones in the third row of the Periodic Table. Make sure that their electron arrangement makes sense before reading on.

28_third orbital elements
The structure of elements 11 through 18, using the Octet Rule

And because they’re also fairly common in living things, we’ll throw in the next two elements, too. In these elements, electrons start filling the fourth energy level.

29_calcium and potassium
The structure of Potassium and Calcium. Note the electrons in the fourth energy level.

 3. Review: Four Things to Know about Drawing Atoms

In this tutorial, we’ve focused on understanding the structure of atoms. We’ve specifically learned that

  1. Electrons are found in energy levels outside the nucleus
  2. The first energy level has a capacity of two electrons
  3. The next two energy levels each have a capacity of 8 electrons.
  4. These rules about electron capacity are known as the Octet rule.

Using these rules, if you’re given the number of protons that an atom has, you should be able to figure out the arrangement of its electrons.

4. Checking Understanding (Flashcards: Atomic Structure)

To check your understanding, we’re going to start with a few flashcards, then move on to an interactive quiz.

[qdeck style=”border: 2px solid black; ” qrecord_id=”sciencemusicvideosMeister1961-Atomic Structure/Drawing Atoms Flashcards (M3)”]

[h] Flashcards: Atomic Structure

[i] Instructions

  • Click ‘Check Answer’ to see the answer to each card.
  • If you know it, click ‘Got it.”
  • If you don’t know it as well as you’d like, click ‘Need more practice,’ and that card will go to the bottom of the deck so you can practice it again.
  • ‘Shuffle’ lets you shuffle the deck.

[!]CARD 1 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] Carbon has 6 protons, 6 neutrons, 6 electrons. On a sheet of paper, draw a carbon atom, then flip the card to see if you drew it correctly.

[a]

 

Carbon’s protons and neutrons go into the nucleus. The first two electrons go into the first energy level. The next four electrons go into the second energy level. To represent how carbon forms chemical bonds, it’s best to draw all four electrons as being unpaired.

[!]CARD 2 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] Sodium has 11 protons, 11 neutrons, 11 electrons. On a sheet of paper, draw a sodium atom, then flip the card to see if you drew it correctly.

[a]

Sodium’s protons and neutrons go into the nucleus. The first two electrons go into the first energy level. The next eight electrons go into the second energy level, and are best shown as four pairs. The last electron goes into the third energy level.

[!]CARD 3 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] Oxygen has 8 protons, 8 neutrons, 8 electrons. On a sheet of paper, draw an oxygen atom, then flip the card to see if you drew it correctly.

[a]

Oxygen’s protons and neutrons go into the nucleus. The first two electrons go into the first energy level. The next six electrons go into the second energy level. The best way to represent the electrons is to draw them as two pairs, and two more single electrons.

[!]CARD 4 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] Phosphorus has 15 protons, 15 neutrons, 15 electrons. On a sheet of paper, draw a phosphorus atom, then flip the card to see if you drew it correctly.

[a]

Phosphorus’s protons and neutrons go into the nucleus. The first two electrons go into the first energy level. The next eight electrons go into the second energy level. The next five electrons go into the third  .

[!]CARD 5 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++[/!]

[q] Potassium has 19 protons, 19 neutrons, 19 electrons. On a sheet of paper, draw a potassium atom, then flip the card to see if you drew it correctly.

[a]

Potassium’s protons and neutrons go into the nucleus. The first two electrons go into the first energy level. The next eight electrons go into the second energy level. The next eight electrons go into the third energy level. The last electron goes into the fourth energy level.

[!]CARD 6 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++[/!]

[q] Nitrogen has 7 protons, 7 neutrons, 7 electrons. On a sheet of paper, draw a nitrogen atom, then flip the card to see if you drew it correctly.

[a]

Nitrogen’s protons and neutrons go into the nucleus. The first two electrons go into the first energy level. The next five electrons go into the second energy level. The best way to represent the electrons is to draw them as one pair, and three single electrons.

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If you want more practice about these terms or concepts, please press the restart button below. Otherwise, continue to the final quiz.

[restart]

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5. Quiz: Structure of Atoms

This quiz tests you on all of the vocabulary you’ve learned so far. It also tests you on your ability to correctly identify an atom’s structure.

[qwiz style = “border: 3px solid black; ” qrecord_id=”sciencemusicvideosMeister1961-Atomic Structure/Drawing Atoms Quiz (M3)”]

[h] QUIZ: Structure of Atoms
[i] This quiz covers key concepts and terms related to the structure of atoms.

Here’s how it works.

  • The quiz consists of a series of multiple choice questions, but it behaves like a stack of flashcards.
  • If you get a question right, you move on to the next question.
  • If you get a question wrong, you’ll get an explanation, and then that question goes to the bottom of the stack.
  • To exit the quiz, you have to answer each question correctly.

[!]QUESTION 1 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] The building block of matter is the

[c] nucleus

[c*] atom

[c] proton

[c] electron

[f] No. The nucleus is the central part of the building block of matter. What would you call the unit that makes up the nucleus plus the electrons?

[f] Correct. Atoms are the building blocks of matter.

[f] No. Protons are found in the nucleus. What would you call the unit that makes up the nucleus plus the electrons?

[f] No. Electrons orbit outside the nucleus. What would you call the unit that makes up the nucleus plus the electrons?

[!]QUESTION 2 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] Almost all of an atom’s mass is in the

[c] protons

[c] neutrons

[c*] nucleus

[c] electron energy levels

[f] No. Protons do make up a significant part of an atom’s mass, but a better answer would be the part that includes both protons and neutrons. What part of the atom is that?

[f] No. Neutrons do make up a significant part of an atom’s mass, but a better answer would be the part that includes both protons and neutrons. What part of the atom is that?

[f] Yes. Almost all of an atom’s mass is found in the nucleus, which consists of protons and neutrons.

[f] No. An energy level is the region outside of the nucleus where electrons are found. Where do you find the protons and neutrons, the most massive particles in an atom?

[!]QUESTION 3 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] The two particles found in the atom’s nucleus are the

[c*] neutron and proton

[c] neutron and electron

[c] proton and electron

[f] Correct. Neutrons and protons make up the atom’s nucleus.

[f] No. Neutrons are found in the nucleus, but not electrons. The second particle is one with a positive charge.

[f] No. Protons are found in the nucleus, but not electrons. The second particle is the one with a neutral charge. 

[!]QUESTION 4 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] The positively charged particle in an atom is the

[c] electron

[c*] proton

[c] neutron

[f] No. Electrons have a negative charge. The positively charged particle is found in the nucleus.

[f] Correct. The positively charged particle in the atom is the proton.

[f] No. Neutrons have no charge (making them neutral). The positively charged particle is the other particle (besides the neutron) in the nucleus.

[!]QUESTION 5 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] The negatively charged particle in an atom is the

[c*] electron

[c] proton

[c] neutron

[f] Yes. Electrons have a negative charge.

[f] No. Protons have a positive charge. The negatively charged particle in the atom is the one outside the nucleus.

[f] No. Neutrons have no charge (making them neutral). The negatively charged particle in the atom is the one outside the nucleus.

[!]QUESTION 6 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] The particle in an atom that has no charge is the

[c] electron

[c] proton

[c*] neutron

[f]  No. Electrons have a negative charge.

[f] No. Protons have a positive charge. The particle without any charge is the other particle (besides the proton) in the nucleus.

[f] Exactly. Neutrons have no charge (making them neutral).

[!]QUESTION 7 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] Electrons are found in

[c] the nucleus

[c*] energy levels or shells

[f] No. The nucleus is the central part of the atom, where protons and neutrons are found.

[f] Correct. Electrons are found in energy levels (also called shells)

[!]QUESTION 8 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] Of the terms below, the one most similar to “orbit” is

[c*] energy level

[c] nucleus

[f] Yes. The terms ‘energy level’ and ‘orbit’ both refer to the region outside of the nucleus where electrons are found.

[f] No. The nucleus is the central region of the atom, where protons and neutrons are found. You’re looking for a term that refers to where electrons are found.

[!]QUESTION 9 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] In an uncharged atom, the number of protons is equal to the number of

[c] energy levels

[c] shells

[c] neutrons

[c*] electrons

[f] No. While it’s possible for the number of protons to equal the number of energy levels, it’s not a necessary relationship. Think about a particle whose charge is the opposite of the proton’s.

[f] No. While it’s possible for the number of protons to equal the number of electron shells, it’s not a necessary relationship. Think about a particle whose charge is the opposite of the proton’s.

[f] No. While it’s not uncommon for the number of protons to equal the number of neutrons, the number can also be different. Think about a particle whose charge is the opposite of the proton’s.

[f] Excellent! In an uncharged atom, the number of protons is equal to the number of electrons.

[!]QUESTION 10 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] An element is composed of

[c*] Only one type of atom

[c] At least two types of atoms

[c] Only atoms that have lost their electrons

[f] Yes. An element is a substance that is composed of only one type of atom.

[f] No. Substances composed of two or more types of atoms are compounds (and we’ll learn more about them later.

[f] No. While an atom might temporarily lose its electrons (more about that later), there are no substances that are composed of atoms that have lost their electrons.

[!]QUESTION 11 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] Which of the following could NOT be the chemical symbol for an element

[c] Fe

[c*] Heg

[c] I

[c] Mn

[f] No. Chemical symbols consist of one or two letters. The first (or only) letter is capitalized. The second letter is lower case. “Fe” is a perfectly legitimate symbol…the symbol for the letter Iron.

[f] Yes: “Heg” could NOT be a chemical symbol for an element. Chemical symbols consist of one or two letters. The first (or only) letter is capitalized. The second letter is lower case. With three letters, “Heg” is not a legitimate chemical symbol. 

[f] No. Chemical symbols consist of one or two letters. The first (or only) letter is capitalized. The second letter is lower case. “I” is a perfectly legitimate symbol…the symbol for the element Iodine.

[f] No. Chemical symbols consist of one or two letters. The first (or only) letter is capitalized. The second letter is lower case. “Mn” is a perfectly legitimate symbol…the symbol for the element Manganese

[!]QUESTION 12 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] Nitrogen has 7 protons, 7 neutrons, and 7 electrons. Following the Octet Rule for placing electrons in energy levels, which of the following arrangements is correct?

[c] All seven electrons in the first energy level. 

[c] Three electrons in the first energy level , four electrons in the second energy level. 

[c*] Two electrons in the first energy level, five in the second energy level. 

[f] No. To represent the structure of the electrons in an atom, keep in mind the capacity of each energy level (two electrons in the first, eight in the  second, and eight in the third. In Nitrogen, with seven electrons, the first two electrons need to go into the first energy level. That leaves five electrons for the second energy level.

[f] No. To represent the structure of the electrons in an atom, keep in mind the capacity of each energy level (two electrons in the first, eight in the  second, and eight in the third. In Nitrogen, with seven electrons, the first two electrons need to go into the first energy level. That leaves five electrons for the second energy level.

[f] Correct. In Nitrogen, with seven electrons, the first two electrons need to go into the first energy level. That leaves five electrons for the second energy level.

[!]QUESTION 13 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] Sulfur has 16 protons, 16 neutrons, and 16 electrons. Following the Octet Rule for placing electrons in energy level, which of the following arrangements is correct?

[c*] Two electrons in the first energy level, eight electrons in the second energy level, and six in the third energy level.

[c] Eight electrons in the first energy level, eight electrons in the second energy level. 

[c] Six electrons in the first energy level, six in the second energy level, and four in the third. 

[f] Excellent. In Sulfur, with 16 electrons, the first two electrons go in the first energy level, the next 8 in the second energy level, and the last six in the third energy level.

[f] No. To represent the structure of electrons in atoms, keep in mind the capacity of each energy level (two electrons in the first, eight in the  second, and eight in the third). In sulfur, with 16 electrons, the first two electrons need to go into the first energy level. The next eight would go into the second energy level, which leaves six electrons for the third energy level.

[f] No. To represent the structure of electrons in atoms, keep in mind the capacity of each energy level (two electrons in the first, eight in the  second, and eight in the third). In sulfur, with 16 electrons, the first two electrons need to go into the first energy level. The next eight would go into the second energy level, which leaves six electrons for the third energy level.

[!]QUESTION 14 ++++++++++++++++++++++++++++++++++++++++++++[/!] 

[q] Carbon has 6 protons, 6 neutrons, and 6 electrons. Following the Octet Rule for placing electrons in energy level, which of the following arrangements is correct?

[c] Three electrons in the first energy level, and three in the second.

[c] One electron in the first energy level, and five in the second. 

[c*] Two electrons in the first energy level, and four in the second. 

[f] No. To represent the structure of electrons in atoms, keep in mind the capacity of each energy level (two electrons in the first, eight in the  second, and eight in the third). In Carbon, with 6 electrons, the first two electrons need to go into the first energy level. The next four go into the second energy level.

[f] No. To represent the structure of electrons in atoms, keep in mind the capacity of each energy level (two electrons in the first, eight in the  second, and eight in the third). In Carbon, with 6 electrons, the first two electrons need to go into the first energy level. The next four go into the second energy level.

[f] Excellent. In Carbon, with 6 electrons, the first two electrons go in the first energy level, and the next 4 go into the second energy level.

[!]QUESTION 15 ++++++++++++++++++++++++++++++++++++++++++++[/!]

[q] Potassium has 19 protons, 19 neutrons, and 19 electrons. Following the Octet Rule for placing electrons in energy level, which of the following arrangements is correct?

[c] Ten electrons in the first energy level, nine in the second.

[c*] Two electrons in the first energy level, eight in the second, eight in the third, and one in the fourth.

[c] Two electrons in the first energy level, ten in the second, and seven in the third.

[f] No. To represent the structure of electrons in atoms, keep in mind the capacity of each energy level (two electrons in the first, eight in the  second, and eight in the third). In Potassium, with 19 electrons, the first two electrons go into the first energy level. The next 8 go into the second energy level. The next 8 go into the third energy level. That leaves one electron for the fourth energy level.

[f] Nice job! In Potassium, with 19 electrons, the first two electrons go into the first energy level. The next 8 go into the second energy level. The next 8 go into the third energy level. That leaves one electron for the fourth energy level.

[f] No. To represent the structure of electrons in atoms, keep in mind the capacity of each energy level (two electrons in the first, eight in the  second, and eight in the third). In Potassium, with 19 electrons, the first two electrons go into the first energy level. The next 8 go into the second energy level. The next 8 go into the third energy level. That leaves one electron for the fourth energy level. 

[x]
If you want to take this quiz again, click the button below

[restart]

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6. Next steps

If you need more practice, please scroll up to the top and work through this tutorial again. Otherwise, follow the links below: